windows-server-2003/tools/perl/lib/pod/perlfunc.pod


								=head1 NAME


								perlfunc - Perl builtin functions


								=head1 DESCRIPTION


								The functions in this section can serve as terms in an expression.

								They fall into two major categories: list operators and named unary

								operators.  These differ in their precedence relationship with a

								following comma.  (See the precedence table in L<perlop>.)  List

								operators take more than one argument, while unary operators can never

								take more than one argument.  Thus, a comma terminates the argument of

								a unary operator, but merely separates the arguments of a list

								operator.  A unary operator generally provides a scalar context to its

								argument, while a list operator may provide either scalar or list

								contexts for its arguments.  If it does both, the scalar arguments will

								be first, and the list argument will follow.  (Note that there can ever

								be only one such list argument.)  For instance, splice() has three scalar

								arguments followed by a list, whereas gethostbyname() has four scalar

								arguments.


								In the syntax descriptions that follow, list operators that expect a

								list (and provide list context for the elements of the list) are shown

								with LIST as an argument.  Such a list may consist of any combination

								of scalar arguments or list values; the list values will be included

								in the list as if each individual element were interpolated at that

								point in the list, forming a longer single-dimensional list value.

								Elements of the LIST should be separated by commas.


								Any function in the list below may be used either with or without

								parentheses around its arguments.  (The syntax descriptions omit the

								parentheses.)  If you use the parentheses, the simple (but occasionally

								surprising) rule is this: It I<looks> like a function, therefore it I<is> a

								function, and precedence doesn't matter.  Otherwise it's a list

								operator or unary operator, and precedence does matter.  And whitespace

								between the function and left parenthesis doesn't count--so you need to

								be careful sometimes:


								    print 1+2+4;	# Prints 7.

								    print(1+2) + 4;	# Prints 3.

								    print (1+2)+4;	# Also prints 3!

								    print +(1+2)+4;	# Prints 7.

								    print ((1+2)+4);	# Prints 7.


								If you run Perl with the B<-w> switch it can warn you about this.  For

								example, the third line above produces:


								    print (...) interpreted as function at - line 1.

								    Useless use of integer addition in void context at - line 1.


								A few functions take no arguments at all, and therefore work as neither

								unary nor list operators.  These include such functions as C<time>

								and C<endpwent>.  For example, C<time+86_400> always means

								C<time() + 86_400>.


								For functions that can be used in either a scalar or list context,

								nonabortive failure is generally indicated in a scalar context by

								returning the undefined value, and in a list context by returning the

								null list.


								Remember the following important rule: There is B<no rule> that relates

								the behavior of an expression in list context to its behavior in scalar

								context, or vice versa.  It might do two totally different things.

								Each operator and function decides which sort of value it would be most

								appropriate to return in scalar context.  Some operators return the

								length of the list that would have been returned in list context.  Some

								operators return the first value in the list.  Some operators return the

								last value in the list.  Some operators return a count of successful

								operations.  In general, they do what you want, unless you want

								consistency.


								An named array in scalar context is quite different from what would at

								first glance appear to be a list in scalar context.  You can't get a list

								like C<(1,2,3)> into being in scalar context, because the compiler knows

								the context at compile time.  It would generate the scalar comma operator

								there, not the list construction version of the comma.  That means it

								was never a list to start with.


								In general, functions in Perl that serve as wrappers for system calls

								of the same name (like chown(2), fork(2), closedir(2), etc.) all return

								true when they succeed and C<undef> otherwise, as is usually mentioned

								in the descriptions below.  This is different from the C interfaces,

								which return C<-1> on failure.  Exceptions to this rule are C<wait>,

								C<waitpid>, and C<syscall>.  System calls also set the special C<$!>

								variable on failure.  Other functions do not, except accidentally.


								=head2 Perl Functions by Category


								Here are Perl's functions (including things that look like

								functions, like some keywords and named operators)

								arranged by category.  Some functions appear in more

								than one place.


								=over 4


								=item Functions for SCALARs or strings


								C<chomp>, C<chop>, C<chr>, C<crypt>, C<hex>, C<index>, C<lc>, C<lcfirst>,

								C<length>, C<oct>, C<ord>, C<pack>, C<q/STRING/>, C<qq/STRING/>, C<reverse>,

								C<rindex>, C<sprintf>, C<substr>, C<tr///>, C<uc>, C<ucfirst>, C<y///>


								=item Regular expressions and pattern matching


								C<m//>, C<pos>, C<quotemeta>, C<s///>, C<split>, C<study>, C<qr//>


								=item Numeric functions


								C<abs>, C<atan2>, C<cos>, C<exp>, C<hex>, C<int>, C<log>, C<oct>, C<rand>,

								C<sin>, C<sqrt>, C<srand>


								=item Functions for real @ARRAYs


								C<pop>, C<push>, C<shift>, C<splice>, C<unshift>


								=item Functions for list data


								C<grep>, C<join>, C<map>, C<qw/STRING/>, C<reverse>, C<sort>, C<unpack>


								=item Functions for real %HASHes


								C<delete>, C<each>, C<exists>, C<keys>, C<values>


								=item Input and output functions


								C<binmode>, C<close>, C<closedir>, C<dbmclose>, C<dbmopen>, C<die>, C<eof>,

								C<fileno>, C<flock>, C<format>, C<getc>, C<print>, C<printf>, C<read>,

								C<readdir>, C<rewinddir>, C<seek>, C<seekdir>, C<select>, C<syscall>,

								C<sysread>, C<sysseek>, C<syswrite>, C<tell>, C<telldir>, C<truncate>,

								C<warn>, C<write>


								=item Functions for fixed length data or records


								C<pack>, C<read>, C<syscall>, C<sysread>, C<syswrite>, C<unpack>, C<vec>


								=item Functions for filehandles, files, or directories


								C<-I<X>>, C<chdir>, C<chmod>, C<chown>, C<chroot>, C<fcntl>, C<glob>,

								C<ioctl>, C<link>, C<lstat>, C<mkdir>, C<open>, C<opendir>,

								C<readlink>, C<rename>, C<rmdir>, C<stat>, C<symlink>, C<umask>,

								C<unlink>, C<utime>


								=item Keywords related to the control flow of your perl program


								C<caller>, C<continue>, C<die>, C<do>, C<dump>, C<eval>, C<exit>,

								C<goto>, C<last>, C<next>, C<redo>, C<return>, C<sub>, C<wantarray>


								=item Keywords related to scoping


								C<caller>, C<import>, C<local>, C<my>, C<our>, C<package>, C<use>


								=item Miscellaneous functions


								C<defined>, C<dump>, C<eval>, C<formline>, C<local>, C<my>, C<our>, C<reset>,

								C<scalar>, C<undef>, C<wantarray>


								=item Functions for processes and process groups


								C<alarm>, C<exec>, C<fork>, C<getpgrp>, C<getppid>, C<getpriority>, C<kill>,

								C<pipe>, C<qx/STRING/>, C<setpgrp>, C<setpriority>, C<sleep>, C<system>,

								C<times>, C<wait>, C<waitpid>


								=item Keywords related to perl modules


								C<do>, C<import>, C<no>, C<package>, C<require>, C<use>


								=item Keywords related to classes and object-orientedness


								C<bless>, C<dbmclose>, C<dbmopen>, C<package>, C<ref>, C<tie>, C<tied>,

								C<untie>, C<use>


								=item Low-level socket functions


								C<accept>, C<bind>, C<connect>, C<getpeername>, C<getsockname>,

								C<getsockopt>, C<listen>, C<recv>, C<send>, C<setsockopt>, C<shutdown>,

								C<socket>, C<socketpair>


								=item System V interprocess communication functions


								C<msgctl>, C<msgget>, C<msgrcv>, C<msgsnd>, C<semctl>, C<semget>, C<semop>,

								C<shmctl>, C<shmget>, C<shmread>, C<shmwrite>


								=item Fetching user and group info


								C<endgrent>, C<endhostent>, C<endnetent>, C<endpwent>, C<getgrent>,

								C<getgrgid>, C<getgrnam>, C<getlogin>, C<getpwent>, C<getpwnam>,

								C<getpwuid>, C<setgrent>, C<setpwent>


								=item Fetching network info


								C<endprotoent>, C<endservent>, C<gethostbyaddr>, C<gethostbyname>,

								C<gethostent>, C<getnetbyaddr>, C<getnetbyname>, C<getnetent>,

								C<getprotobyname>, C<getprotobynumber>, C<getprotoent>,

								C<getservbyname>, C<getservbyport>, C<getservent>, C<sethostent>,

								C<setnetent>, C<setprotoent>, C<setservent>


								=item Time-related functions


								C<gmtime>, C<localtime>, C<time>, C<times>


								=item Functions new in perl5


								C<abs>, C<bless>, C<chomp>, C<chr>, C<exists>, C<formline>, C<glob>,

								C<import>, C<lc>, C<lcfirst>, C<map>, C<my>, C<no>, C<our>, C<prototype>,

								C<qx>, C<qw>, C<readline>, C<readpipe>, C<ref>, C<sub*>, C<sysopen>, C<tie>,

								C<tied>, C<uc>, C<ucfirst>, C<untie>, C<use>


								* - C<sub> was a keyword in perl4, but in perl5 it is an

								operator, which can be used in expressions.


								=item Functions obsoleted in perl5


								C<dbmclose>, C<dbmopen>


								=back


								=head2 Portability


								Perl was born in Unix and can therefore access all common Unix

								system calls.  In non-Unix environments, the functionality of some

								Unix system calls may not be available, or details of the available

								functionality may differ slightly.  The Perl functions affected

								by this are:


								C<-X>, C<binmode>, C<chmod>, C<chown>, C<chroot>, C<crypt>,

								C<dbmclose>, C<dbmopen>, C<dump>, C<endgrent>, C<endhostent>,

								C<endnetent>, C<endprotoent>, C<endpwent>, C<endservent>, C<exec>,

								C<fcntl>, C<flock>, C<fork>, C<getgrent>, C<getgrgid>, C<gethostent>,

								C<getlogin>, C<getnetbyaddr>, C<getnetbyname>, C<getnetent>,

								C<getppid>, C<getprgp>, C<getpriority>, C<getprotobynumber>,

								C<getprotoent>, C<getpwent>, C<getpwnam>, C<getpwuid>,

								C<getservbyport>, C<getservent>, C<getsockopt>, C<glob>, C<ioctl>,

								C<kill>, C<link>, C<lstat>, C<msgctl>, C<msgget>, C<msgrcv>,

								C<msgsnd>, C<open>, C<pipe>, C<readlink>, C<rename>, C<select>, C<semctl>,

								C<semget>, C<semop>, C<setgrent>, C<sethostent>, C<setnetent>,

								C<setpgrp>, C<setpriority>, C<setprotoent>, C<setpwent>,

								C<setservent>, C<setsockopt>, C<shmctl>, C<shmget>, C<shmread>,

								C<shmwrite>, C<socket>, C<socketpair>, C<stat>, C<symlink>, C<syscall>,

								C<sysopen>, C<system>, C<times>, C<truncate>, C<umask>, C<unlink>,

								C<utime>, C<wait>, C<waitpid>


								For more information about the portability of these functions, see

								L<perlport> and other available platform-specific documentation.


								=head2 Alphabetical Listing of Perl Functions


								=over 8


								=item I<-X> FILEHANDLE


								=item I<-X> EXPR


								=item I<-X>


								A file test, where X is one of the letters listed below.  This unary

								operator takes one argument, either a filename or a filehandle, and

								tests the associated file to see if something is true about it.  If the

								argument is omitted, tests C<$_>, except for C<-t>, which tests STDIN.

								Unless otherwise documented, it returns C<1> for true and C<''> for false, or

								the undefined value if the file doesn't exist.  Despite the funny

								names, precedence is the same as any other named unary operator, and

								the argument may be parenthesized like any other unary operator.  The

								operator may be any of:

								X<-r>X<-w>X<-x>X<-o>X<-R>X<-W>X<-X>X<-O>X<-e>X<-z>X<-s>X<-f>X<-d>X<-l>X<-p>

								X<-S>X<-b>X<-c>X<-t>X<-u>X<-g>X<-k>X<-T>X<-B>X<-M>X<-A>X<-C>


								    -r	File is readable by effective uid/gid.

								    -w	File is writable by effective uid/gid.

								    -x	File is executable by effective uid/gid.

								    -o	File is owned by effective uid.


								    -R	File is readable by real uid/gid.

								    -W	File is writable by real uid/gid.

								    -X	File is executable by real uid/gid.

								    -O	File is owned by real uid.


								    -e	File exists.

								    -z	File has zero size (is empty).

								    -s	File has nonzero size (returns size in bytes).


								    -f	File is a plain file.

								    -d	File is a directory.

								    -l	File is a symbolic link.

								    -p	File is a named pipe (FIFO), or Filehandle is a pipe.

								    -S	File is a socket.

								    -b	File is a block special file.

								    -c	File is a character special file.

								    -t	Filehandle is opened to a tty.


								    -u	File has setuid bit set.

								    -g	File has setgid bit set.

								    -k	File has sticky bit set.


								    -T	File is an ASCII text file.

								    -B	File is a "binary" file (opposite of -T).


								    -M	Age of file in days when script started.

								    -A	Same for access time.

								    -C	Same for inode change time.


								Example:


								    while (<>) {

									chomp;

									next unless -f $_;	# ignore specials

									#...

								    }


								The interpretation of the file permission operators C<-r>, C<-R>,

								C<-w>, C<-W>, C<-x>, and C<-X> is by default based solely on the mode

								of the file and the uids and gids of the user.  There may be other

								reasons you can't actually read, write, or execute the file.  Such

								reasons may be for example network filesystem access controls, ACLs

								(access control lists), read-only filesystems, and unrecognized

								executable formats.


								Also note that, for the superuser on the local filesystems, the C<-r>,

								C<-R>, C<-w>, and C<-W> tests always return 1, and C<-x> and C<-X> return 1

								if any execute bit is set in the mode.  Scripts run by the superuser

								may thus need to do a stat() to determine the actual mode of the file,

								or temporarily set their effective uid to something else.


								If you are using ACLs, there is a pragma called C<filetest> that may

								produce more accurate results than the bare stat() mode bits.

								When under the C<use filetest 'access'> the above-mentioned filetests

								will test whether the permission can (not) be granted using the

								access() family of system calls.  Also note that the C<-x> and C<-X> may

								under this pragma return true even if there are no execute permission

								bits set (nor any extra execute permission ACLs).  This strangeness is

								due to the underlying system calls' definitions.  Read the

								documentation for the C<filetest> pragma for more information.


								Note that C<-s/a/b/> does not do a negated substitution.  Saying

								C<-exp($foo)> still works as expected, however--only single letters

								following a minus are interpreted as file tests.


								The C<-T> and C<-B> switches work as follows.  The first block or so of the

								file is examined for odd characters such as strange control codes or

								characters with the high bit set.  If too many strange characters (>30%)

								are found, it's a C<-B> file, otherwise it's a C<-T> file.  Also, any file

								containing null in the first block is considered a binary file.  If C<-T>

								or C<-B> is used on a filehandle, the current stdio buffer is examined

								rather than the first block.  Both C<-T> and C<-B> return true on a null

								file, or a file at EOF when testing a filehandle.  Because you have to

								read a file to do the C<-T> test, on most occasions you want to use a C<-f>

								against the file first, as in C<next unless -f $file && -T $file>.


								If any of the file tests (or either the C<stat> or C<lstat> operators) are given

								the special filehandle consisting of a solitary underline, then the stat

								structure of the previous file test (or stat operator) is used, saving

								a system call.  (This doesn't work with C<-t>, and you need to remember

								that lstat() and C<-l> will leave values in the stat structure for the

								symbolic link, not the real file.)  Example:


								    print "Can do.\n" if -r $a || -w _ || -x _;


								    stat($filename);

								    print "Readable\n" if -r _;

								    print "Writable\n" if -w _;

								    print "Executable\n" if -x _;

								    print "Setuid\n" if -u _;

								    print "Setgid\n" if -g _;

								    print "Sticky\n" if -k _;

								    print "Text\n" if -T _;

								    print "Binary\n" if -B _;


								=item abs VALUE


								=item abs


								Returns the absolute value of its argument.

								If VALUE is omitted, uses C<$_>.


								=item accept NEWSOCKET,GENERICSOCKET


								Accepts an incoming socket connect, just as the accept(2) system call

								does.  Returns the packed address if it succeeded, false otherwise.

								See the example in L<perlipc/"Sockets: Client/Server Communication">.


								On systems that support a close-on-exec flag on files, the flag will

								be set for the newly opened file descriptor, as determined by the

								value of $^F.  See L<perlvar/$^F>.


								=item alarm SECONDS


								=item alarm


								Arranges to have a SIGALRM delivered to this process after the

								specified number of seconds have elapsed.  If SECONDS is not specified,

								the value stored in C<$_> is used. (On some machines,

								unfortunately, the elapsed time may be up to one second less than you

								specified because of how seconds are counted.)  Only one timer may be

								counting at once.  Each call disables the previous timer, and an

								argument of C<0> may be supplied to cancel the previous timer without

								starting a new one.  The returned value is the amount of time remaining

								on the previous timer.


								For delays of finer granularity than one second, you may use Perl's

								four-argument version of select() leaving the first three arguments

								undefined, or you might be able to use the C<syscall> interface to

								access setitimer(2) if your system supports it.  The Time::HiRes module

								from CPAN may also prove useful.


								It is usually a mistake to intermix C<alarm> and C<sleep> calls.

								(C<sleep> may be internally implemented in your system with C<alarm>)


								If you want to use C<alarm> to time out a system call you need to use an

								C<eval>/C<die> pair.  You can't rely on the alarm causing the system call to

								fail with C<$!> set to C<EINTR> because Perl sets up signal handlers to

								restart system calls on some systems.  Using C<eval>/C<die> always works,

								modulo the caveats given in L<perlipc/"Signals">.


								    eval {

									local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required

									alarm $timeout;

									$nread = sysread SOCKET, $buffer, $size;

									alarm 0;

								    };

								    if ($@) {

									die unless $@ eq "alarm\n";   # propagate unexpected errors

								    	# timed out

								    }

								    else {

								    	# didn't

								    }


								=item atan2 Y,X


								Returns the arctangent of Y/X in the range -PI to PI.


								For the tangent operation, you may use the C<Math::Trig::tan>

								function, or use the familiar relation:


								    sub tan { sin($_[0]) / cos($_[0])  }


								=item bind SOCKET,NAME


								Binds a network address to a socket, just as the bind system call

								does.  Returns true if it succeeded, false otherwise.  NAME should be a

								packed address of the appropriate type for the socket.  See the examples in

								L<perlipc/"Sockets: Client/Server Communication">.


								=item binmode FILEHANDLE, DISCIPLINE


								=item binmode FILEHANDLE


								Arranges for FILEHANDLE to be read or written in "binary" or "text" mode

								on systems where the run-time libraries distinguish between binary and

								text files.  If FILEHANDLE is an expression, the value is taken as the

								name of the filehandle.  DISCIPLINE can be either of C<":raw"> for

								binary mode or C<":crlf"> for "text" mode.  If the DISCIPLINE is

								omitted, it defaults to C<":raw">.


								binmode() should be called after open() but before any I/O is done on

								the filehandle.


								On many systems binmode() currently has no effect, but in future, it

								will be extended to support user-defined input and output disciplines.

								On some systems binmode() is necessary when you're not working with a

								text file.  For the sake of portability it is a good idea to always use

								it when appropriate, and to never use it when it isn't appropriate.


								In other words:  Regardless of platform, use binmode() on binary

								files, and do not use binmode() on text files.


								The C<open> pragma can be used to establish default disciplines.

								See L<open>.


								The operating system, device drivers, C libraries, and Perl run-time

								system all work together to let the programmer treat a single

								character (C<\n>) as the line terminator, irrespective of the external

								representation.  On many operating systems, the native text file

								representation matches the internal representation, but on some

								platforms the external representation of C<\n> is made up of more than

								one character.


								Mac OS and all variants of Unix use a single character to end each line

								in the external representation of text (even though that single

								character is not necessarily the same across these platforms).

								Consequently binmode() has no effect on these operating systems.  In

								other systems like VMS, MS-DOS and the various flavors of MS-Windows

								your program sees a C<\n> as a simple C<\cJ>, but what's stored in text

								files are the two characters C<\cM\cJ>.  That means that, if you don't

								use binmode() on these systems, C<\cM\cJ> sequences on disk will be

								converted to C<\n> on input, and any C<\n> in your program will be

								converted back to C<\cM\cJ> on output.  This is what you want for text

								files, but it can be disastrous for binary files.


								Another consequence of using binmode() (on some systems) is that

								special end-of-file markers will be seen as part of the data stream.

								For systems from the Microsoft family this means that if your binary

								data contains C<\cZ>, the I/O subsystem will regard it as the end of

								the file, unless you use binmode().


								binmode() is not only important for readline() and print() operations,

								but also when using read(), seek(), sysread(), syswrite() and tell()

								(see L<perlport> for more details).  See the C<$/> and C<$\> variables

								in L<perlvar> for how to manually set your input and output

								line-termination sequences.


								=item bless REF,CLASSNAME


								=item bless REF


								This function tells the thingy referenced by REF that it is now an object

								in the CLASSNAME package.  If CLASSNAME is omitted, the current package

								is used.  Because a C<bless> is often the last thing in a constructor,

								it returns the reference for convenience.  Always use the two-argument

								version if the function doing the blessing might be inherited by a

								derived class.  See L<perltoot> and L<perlobj> for more about the blessing

								(and blessings) of objects.


								Consider always blessing objects in CLASSNAMEs that are mixed case.

								Namespaces with all lowercase names are considered reserved for

								Perl pragmata.  Builtin types have all uppercase names, so to prevent

								confusion, you may wish to avoid such package names as well.  Make sure

								that CLASSNAME is a true value.


								See L<perlmod/"Perl Modules">.


								=item caller EXPR


								=item caller


								Returns the context of the current subroutine call.  In scalar context,

								returns the caller's package name if there is a caller, that is, if

								we're in a subroutine or C<eval> or C<require>, and the undefined value

								otherwise.  In list context, returns


								    ($package, $filename, $line) = caller;


								With EXPR, it returns some extra information that the debugger uses to

								print a stack trace.  The value of EXPR indicates how many call frames

								to go back before the current one.


								    ($package, $filename, $line, $subroutine, $hasargs,

								    $wantarray, $evaltext, $is_require, $hints, $bitmask) = caller($i);


								Here $subroutine may be C<(eval)> if the frame is not a subroutine

								call, but an C<eval>.  In such a case additional elements $evaltext and

								C<$is_require> are set: C<$is_require> is true if the frame is created by a

								C<require> or C<use> statement, $evaltext contains the text of the

								C<eval EXPR> statement.  In particular, for an C<eval BLOCK> statement,

								$filename is C<(eval)>, but $evaltext is undefined.  (Note also that

								each C<use> statement creates a C<require> frame inside an C<eval EXPR>)

								frame.  C<$hasargs> is true if a new instance of C<@_> was set up for the

								frame.  C<$hints> and C<$bitmask> contain pragmatic hints that the caller

								was compiled with.  The C<$hints> and C<$bitmask> values are subject to

								change between versions of Perl, and are not meant for external use.


								Furthermore, when called from within the DB package, caller returns more

								detailed information: it sets the list variable C<@DB::args> to be the

								arguments with which the subroutine was invoked.


								Be aware that the optimizer might have optimized call frames away before

								C<caller> had a chance to get the information.  That means that C<caller(N)>

								might not return information about the call frame you expect it do, for

								C<< N > 1 >>.  In particular, C<@DB::args> might have information from the

								previous time C<caller> was called.


								=item chdir EXPR


								Changes the working directory to EXPR, if possible.  If EXPR is omitted,

								changes to the directory specified by C<$ENV{HOME}>, if set; if not,

								changes to the directory specified by C<$ENV{LOGDIR}>.  If neither is

								set, C<chdir> does nothing.  It returns true upon success, false

								otherwise.  See the example under C<die>.


								=item chmod LIST


								Changes the permissions of a list of files.  The first element of the

								list must be the numerical mode, which should probably be an octal

								number, and which definitely should I<not> a string of octal digits:

								C<0644> is okay, C<'0644'> is not.  Returns the number of files

								successfully changed.  See also L</oct>, if all you have is a string.


								    $cnt = chmod 0755, 'foo', 'bar';

								    chmod 0755, @executables;

								    $mode = '0644'; chmod $mode, 'foo';      # !!! sets mode to

								                                             # --w----r-T

								    $mode = '0644'; chmod oct($mode), 'foo'; # this is better

								    $mode = 0644;   chmod $mode, 'foo';      # this is best


								You can also import the symbolic C<S_I*> constants from the Fcntl

								module:


								    use Fcntl ':mode';


								    chmod S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH, @executables;

								    # This is identical to the chmod 0755 of the above example.


								=item chomp VARIABLE


								=item chomp LIST


								=item chomp


								This safer version of L</chop> removes any trailing string

								that corresponds to the current value of C<$/> (also known as

								$INPUT_RECORD_SEPARATOR in the C<English> module).  It returns the total

								number of characters removed from all its arguments.  It's often used to

								remove the newline from the end of an input record when you're worried

								that the final record may be missing its newline.  When in paragraph

								mode (C<$/ = "">), it removes all trailing newlines from the string.

								When in slurp mode (C<$/ = undef>) or fixed-length record mode (C<$/> is

								a reference to an integer or the like, see L<perlvar>) chomp() won't

								remove anything.

								If VARIABLE is omitted, it chomps C<$_>.  Example:


								    while (<>) {

									chomp;	# avoid \n on last field

									@array = split(/:/);

									# ...

								    }


								If VARIABLE is a hash, it chomps the hash's values, but not its keys.


								You can actually chomp anything that's an lvalue, including an assignment:


								    chomp($cwd = `pwd`);

								    chomp($answer = <STDIN>);


								If you chomp a list, each element is chomped, and the total number of

								characters removed is returned.


								=item chop VARIABLE


								=item chop LIST


								=item chop


								Chops off the last character of a string and returns the character

								chopped.  It is much more efficient than C<s/.$//s> because it neither

								scans nor copies the string.  If VARIABLE is omitted, chops C<$_>.

								If VARIABLE is a hash, it chops the hash's values, but not its keys.


								You can actually chop anything that's an lvalue, including an assignment.


								If you chop a list, each element is chopped.  Only the value of the

								last C<chop> is returned.


								Note that C<chop> returns the last character.  To return all but the last

								character, use C<substr($string, 0, -1)>.


								=item chown LIST


								Changes the owner (and group) of a list of files.  The first two

								elements of the list must be the I<numeric> uid and gid, in that

								order.  A value of -1 in either position is interpreted by most

								systems to leave that value unchanged.  Returns the number of files

								successfully changed.


								    $cnt = chown $uid, $gid, 'foo', 'bar';

								    chown $uid, $gid, @filenames;


								Here's an example that looks up nonnumeric uids in the passwd file:


								    print "User: ";

								    chomp($user = <STDIN>);

								    print "Files: ";

								    chomp($pattern = <STDIN>);


								    ($login,$pass,$uid,$gid) = getpwnam($user)

									or die "$user not in passwd file";


								    @ary = glob($pattern);	# expand filenames

								    chown $uid, $gid, @ary;


								On most systems, you are not allowed to change the ownership of the

								file unless you're the superuser, although you should be able to change

								the group to any of your secondary groups.  On insecure systems, these

								restrictions may be relaxed, but this is not a portable assumption.

								On POSIX systems, you can detect this condition this way:


								    use POSIX qw(sysconf _PC_CHOWN_RESTRICTED);

								    $can_chown_giveaway = not sysconf(_PC_CHOWN_RESTRICTED);


								=item chr NUMBER


								=item chr


								Returns the character represented by that NUMBER in the character set.

								For example, C<chr(65)> is C<"A"> in either ASCII or Unicode, and

								chr(0x263a) is a Unicode smiley face (but only within the scope of

								a C<use utf8>).  For the reverse, use L</ord>.

								See L<utf8> for more about Unicode.


								If NUMBER is omitted, uses C<$_>.


								=item chroot FILENAME


								=item chroot


								This function works like the system call by the same name: it makes the

								named directory the new root directory for all further pathnames that

								begin with a C</> by your process and all its children.  (It doesn't

								change your current working directory, which is unaffected.)  For security

								reasons, this call is restricted to the superuser.  If FILENAME is

								omitted, does a C<chroot> to C<$_>.


								=item close FILEHANDLE


								=item close


								Closes the file or pipe associated with the file handle, returning true

								only if stdio successfully flushes buffers and closes the system file

								descriptor.  Closes the currently selected filehandle if the argument

								is omitted.


								You don't have to close FILEHANDLE if you are immediately going to do

								another C<open> on it, because C<open> will close it for you.  (See

								C<open>.)  However, an explicit C<close> on an input file resets the line

								counter (C<$.>), while the implicit close done by C<open> does not.


								If the file handle came from a piped open C<close> will additionally

								return false if one of the other system calls involved fails or if the

								program exits with non-zero status.  (If the only problem was that the

								program exited non-zero C<$!> will be set to C<0>.)  Closing a pipe

								also waits for the process executing on the pipe to complete, in case you

								want to look at the output of the pipe afterwards, and

								implicitly puts the exit status value of that command into C<$?>.


								Prematurely closing the read end of a pipe (i.e. before the process

								writing to it at the other end has closed it) will result in a

								SIGPIPE being delivered to the writer.  If the other end can't

								handle that, be sure to read all the data before closing the pipe.


								Example:


								    open(OUTPUT, '|sort >foo')  # pipe to sort

								        or die "Can't start sort: $!";

								    #...			# print stuff to output

								    close OUTPUT		# wait for sort to finish

								        or warn $! ? "Error closing sort pipe: $!"

								                   : "Exit status $? from sort";

								    open(INPUT, 'foo')		# get sort's results

								        or die "Can't open 'foo' for input: $!";


								FILEHANDLE may be an expression whose value can be used as an indirect

								filehandle, usually the real filehandle name.


								=item closedir DIRHANDLE


								Closes a directory opened by C<opendir> and returns the success of that

								system call.


								DIRHANDLE may be an expression whose value can be used as an indirect

								dirhandle, usually the real dirhandle name.


								=item connect SOCKET,NAME


								Attempts to connect to a remote socket, just as the connect system call

								does.  Returns true if it succeeded, false otherwise.  NAME should be a

								packed address of the appropriate type for the socket.  See the examples in

								L<perlipc/"Sockets: Client/Server Communication">.


								=item continue BLOCK


								Actually a flow control statement rather than a function.  If there is a

								C<continue> BLOCK attached to a BLOCK (typically in a C<while> or

								C<foreach>), it is always executed just before the conditional is about to

								be evaluated again, just like the third part of a C<for> loop in C.  Thus

								it can be used to increment a loop variable, even when the loop has been

								continued via the C<next> statement (which is similar to the C C<continue>

								statement).


								C<last>, C<next>, or C<redo> may appear within a C<continue>

								block.  C<last> and C<redo> will behave as if they had been executed within

								the main block.  So will C<next>, but since it will execute a C<continue>

								block, it may be more entertaining.


								    while (EXPR) {

									### redo always comes here

									do_something;

								    } continue {

									### next always comes here

									do_something_else;

									# then back the top to re-check EXPR

								    }

								    ### last always comes here


								Omitting the C<continue> section is semantically equivalent to using an

								empty one, logically enough.  In that case, C<next> goes directly back

								to check the condition at the top of the loop.


								=item cos EXPR


								=item cos


								Returns the cosine of EXPR (expressed in radians).  If EXPR is omitted,

								takes cosine of C<$_>.


								For the inverse cosine operation, you may use the C<Math::Trig::acos()>

								function, or use this relation:


								    sub acos { atan2( sqrt(1 - $_[0] * $_[0]), $_[0] ) }


								=item crypt PLAINTEXT,SALT


								Encrypts a string exactly like the crypt(3) function in the C library

								(assuming that you actually have a version there that has not been

								extirpated as a potential munition).  This can prove useful for checking

								the password file for lousy passwords, amongst other things.  Only the

								guys wearing white hats should do this.


								Note that C<crypt> is intended to be a one-way function, much like breaking

								eggs to make an omelette.  There is no (known) corresponding decrypt

								function.  As a result, this function isn't all that useful for

								cryptography.  (For that, see your nearby CPAN mirror.)


								When verifying an existing encrypted string you should use the encrypted

								text as the salt (like C<crypt($plain, $crypted) eq $crypted>).  This

								allows your code to work with the standard C<crypt> and with more

								exotic implementations.  When choosing a new salt create a random two

								character string whose characters come from the set C<[./0-9A-Za-z]>

								(like C<join '', ('.', '/', 0..9, 'A'..'Z', 'a'..'z')[rand 64, rand 64]>).


								Here's an example that makes sure that whoever runs this program knows

								their own password:


								    $pwd = (getpwuid($<))[1];


								    system "stty -echo";

								    print "Password: ";

								    chomp($word = <STDIN>);

								    print "\n";

								    system "stty echo";


								    if (crypt($word, $pwd) ne $pwd) {

									die "Sorry...\n";

								    } else {

									print "ok\n";

								    }


								Of course, typing in your own password to whoever asks you

								for it is unwise.


								The L<crypt> function is unsuitable for encrypting large quantities

								of data, not least of all because you can't get the information

								back.  Look at the F<by-module/Crypt> and F<by-module/PGP> directories

								on your favorite CPAN mirror for a slew of potentially useful

								modules.


								=item dbmclose HASH


								[This function has been largely superseded by the C<untie> function.]


								Breaks the binding between a DBM file and a hash.


								=item dbmopen HASH,DBNAME,MASK


								[This function has been largely superseded by the C<tie> function.]


								This binds a dbm(3), ndbm(3), sdbm(3), gdbm(3), or Berkeley DB file to a

								hash.  HASH is the name of the hash.  (Unlike normal C<open>, the first

								argument is I<not> a filehandle, even though it looks like one).  DBNAME

								is the name of the database (without the F<.dir> or F<.pag> extension if

								any).  If the database does not exist, it is created with protection

								specified by MASK (as modified by the C<umask>).  If your system supports

								only the older DBM functions, you may perform only one C<dbmopen> in your

								program.  In older versions of Perl, if your system had neither DBM nor

								ndbm, calling C<dbmopen> produced a fatal error; it now falls back to

								sdbm(3).


								If you don't have write access to the DBM file, you can only read hash

								variables, not set them.  If you want to test whether you can write,

								either use file tests or try setting a dummy hash entry inside an C<eval>,

								which will trap the error.


								Note that functions such as C<keys> and C<values> may return huge lists

								when used on large DBM files.  You may prefer to use the C<each>

								function to iterate over large DBM files.  Example:


								    # print out history file offsets

								    dbmopen(%HIST,'/usr/lib/news/history',0666);

								    while (($key,$val) = each %HIST) {

									print $key, ' = ', unpack('L',$val), "\n";

								    }

								    dbmclose(%HIST);


								See also L<AnyDBM_File> for a more general description of the pros and

								cons of the various dbm approaches, as well as L<DB_File> for a particularly

								rich implementation.


								You can control which DBM library you use by loading that library

								before you call dbmopen():


								    use DB_File;

								    dbmopen(%NS_Hist, "$ENV{HOME}/.netscape/history.db")

									or die "Can't open netscape history file: $!";


								=item defined EXPR


								=item defined


								Returns a Boolean value telling whether EXPR has a value other than

								the undefined value C<undef>.  If EXPR is not present, C<$_> will be

								checked.


								Many operations return C<undef> to indicate failure, end of file,

								system error, uninitialized variable, and other exceptional

								conditions.  This function allows you to distinguish C<undef> from

								other values.  (A simple Boolean test will not distinguish among

								C<undef>, zero, the empty string, and C<"0">, which are all equally

								false.)  Note that since C<undef> is a valid scalar, its presence

								doesn't I<necessarily> indicate an exceptional condition: C<pop>

								returns C<undef> when its argument is an empty array, I<or> when the

								element to return happens to be C<undef>.


								You may also use C<defined(&func)> to check whether subroutine C<&func>

								has ever been defined.  The return value is unaffected by any forward

								declarations of C<&foo>.  Note that a subroutine which is not defined

								may still be callable: its package may have an C<AUTOLOAD> method that

								makes it spring into existence the first time that it is called -- see

								L<perlsub>.


								Use of C<defined> on aggregates (hashes and arrays) is deprecated.  It

								used to report whether memory for that aggregate has ever been

								allocated.  This behavior may disappear in future versions of Perl.

								You should instead use a simple test for size:


								    if (@an_array) { print "has array elements\n" }

								    if (%a_hash)   { print "has hash members\n"   }


								When used on a hash element, it tells you whether the value is defined,

								not whether the key exists in the hash.  Use L</exists> for the latter

								purpose.


								Examples:


								    print if defined $switch{'D'};

								    print "$val\n" while defined($val = pop(@ary));

								    die "Can't readlink $sym: $!"

									unless defined($value = readlink $sym);

								    sub foo { defined &$bar ? &$bar(@_) : die "No bar"; }

								    $debugging = 0 unless defined $debugging;


								Note:  Many folks tend to overuse C<defined>, and then are surprised to

								discover that the number C<0> and C<""> (the zero-length string) are, in fact,

								defined values.  For example, if you say


								    "ab" =~ /a(.*)b/;


								The pattern match succeeds, and C<$1> is defined, despite the fact that it

								matched "nothing".  But it didn't really match nothing--rather, it

								matched something that happened to be zero characters long.  This is all

								very above-board and honest.  When a function returns an undefined value,

								it's an admission that it couldn't give you an honest answer.  So you

								should use C<defined> only when you're questioning the integrity of what

								you're trying to do.  At other times, a simple comparison to C<0> or C<""> is

								what you want.


								See also L</undef>, L</exists>, L</ref>.


								=item delete EXPR


								Given an expression that specifies a hash element, array element, hash slice,

								or array slice, deletes the specified element(s) from the hash or array.

								In the case of an array, if the array elements happen to be at the end,

								the size of the array will shrink to the highest element that tests

								true for exists() (or 0 if no such element exists).


								Returns each element so deleted or the undefined value if there was no such

								element.  Deleting from C<$ENV{}> modifies the environment.  Deleting from

								a hash tied to a DBM file deletes the entry from the DBM file.  Deleting

								from a C<tie>d hash or array may not necessarily return anything.


								Deleting an array element effectively returns that position of the array

								to its initial, uninitialized state.  Subsequently testing for the same

								element with exists() will return false.  Note that deleting array

								elements in the middle of an array will not shift the index of the ones

								after them down--use splice() for that.  See L</exists>.


								The following (inefficiently) deletes all the values of %HASH and @ARRAY:


								    foreach $key (keys %HASH) {

									delete $HASH{$key};

								    }


								    foreach $index (0 .. $#ARRAY) {

									delete $ARRAY[$index];

								    }


								And so do these:


								    delete @HASH{keys %HASH};


								    delete @ARRAY[0 .. $#ARRAY];


								But both of these are slower than just assigning the empty list

								or undefining %HASH or @ARRAY:


								    %HASH = ();		# completely empty %HASH

								    undef %HASH;	# forget %HASH ever existed


								    @ARRAY = ();	# completely empty @ARRAY

								    undef @ARRAY;	# forget @ARRAY ever existed


								Note that the EXPR can be arbitrarily complicated as long as the final

								operation is a hash element, array element,  hash slice, or array slice

								lookup:


								    delete $ref->[$x][$y]{$key};

								    delete @{$ref->[$x][$y]}{$key1, $key2, @morekeys};


								    delete $ref->[$x][$y][$index];

								    delete @{$ref->[$x][$y]}[$index1, $index2, @moreindices];


								=item die LIST


								Outside an C<eval>, prints the value of LIST to C<STDERR> and

								exits with the current value of C<$!> (errno).  If C<$!> is C<0>,

								exits with the value of C<<< ($? >> 8) >>> (backtick `command`

								status).  If C<<< ($? >> 8) >>> is C<0>, exits with C<255>.  Inside

								an C<eval(),> the error message is stuffed into C<$@> and the

								C<eval> is terminated with the undefined value.  This makes

								C<die> the way to raise an exception.


								Equivalent examples:


								    die "Can't cd to spool: $!\n" unless chdir '/usr/spool/news';

								    chdir '/usr/spool/news' or die "Can't cd to spool: $!\n"


								If the value of EXPR does not end in a newline, the current script line

								number and input line number (if any) are also printed, and a newline

								is supplied.  Note that the "input line number" (also known as "chunk")

								is subject to whatever notion of "line" happens to be currently in

								effect, and is also available as the special variable C<$.>.

								See L<perlvar/"$/"> and L<perlvar/"$.">.


								Hint: sometimes appending C<", stopped"> to your message

								will cause it to make better sense when the string C<"at foo line 123"> is

								appended.  Suppose you are running script "canasta".


								    die "/etc/games is no good";

								    die "/etc/games is no good, stopped";


								produce, respectively


								    /etc/games is no good at canasta line 123.

								    /etc/games is no good, stopped at canasta line 123.


								See also exit(), warn(), and the Carp module.


								If LIST is empty and C<$@> already contains a value (typically from a

								previous eval) that value is reused after appending C<"\t...propagated">.

								This is useful for propagating exceptions:


								    eval { ... };

								    die unless $@ =~ /Expected exception/;


								If C<$@> is empty then the string C<"Died"> is used.


								die() can also be called with a reference argument.  If this happens to be

								trapped within an eval(), $@ contains the reference.  This behavior permits

								a more elaborate exception handling implementation using objects that

								maintain arbitrary state about the nature of the exception.  Such a scheme

								is sometimes preferable to matching particular string values of $@ using

								regular expressions.  Here's an example:


								    eval { ... ; die Some::Module::Exception->new( FOO => "bar" ) };

								    if ($@) {

								        if (ref($@) && UNIVERSAL::isa($@,"Some::Module::Exception")) {

								            # handle Some::Module::Exception

								        }

								        else {

								            # handle all other possible exceptions

								        }

								    }


								Because perl will stringify uncaught exception messages before displaying

								them, you may want to overload stringification operations on such custom

								exception objects.  See L<overload> for details about that.


								You can arrange for a callback to be run just before the C<die>

								does its deed, by setting the C<$SIG{__DIE__}> hook.  The associated

								handler will be called with the error text and can change the error

								message, if it sees fit, by calling C<die> again.  See

								L<perlvar/$SIG{expr}> for details on setting C<%SIG> entries, and

								L<"eval BLOCK"> for some examples.  Although this feature was meant

								to be run only right before your program was to exit, this is not

								currently the case--the C<$SIG{__DIE__}> hook is currently called

								even inside eval()ed blocks/strings!  If one wants the hook to do

								nothing in such situations, put


									die @_ if $^S;


								as the first line of the handler (see L<perlvar/$^S>).  Because

								this promotes strange action at a distance, this counterintuitive

								behavior may be fixed in a future release.


								=item do BLOCK


								Not really a function.  Returns the value of the last command in the

								sequence of commands indicated by BLOCK.  When modified by a loop

								modifier, executes the BLOCK once before testing the loop condition.

								(On other statements the loop modifiers test the conditional first.)


								C<do BLOCK> does I<not> count as a loop, so the loop control statements

								C<next>, C<last>, or C<redo> cannot be used to leave or restart the block.

								See L<perlsyn> for alternative strategies.


								=item do SUBROUTINE(LIST)


								A deprecated form of subroutine call.  See L<perlsub>.


								=item do EXPR


								Uses the value of EXPR as a filename and executes the contents of the

								file as a Perl script.  Its primary use is to include subroutines

								from a Perl subroutine library.


								    do 'stat.pl';


								is just like


								    scalar eval `cat stat.pl`;


								except that it's more efficient and concise, keeps track of the current

								filename for error messages, searches the @INC libraries, and updates

								C<%INC> if the file is found.  See L<perlvar/Predefined Names> for these

								variables.  It also differs in that code evaluated with C<do FILENAME>

								cannot see lexicals in the enclosing scope; C<eval STRING> does.  It's the

								same, however, in that it does reparse the file every time you call it,

								so you probably don't want to do this inside a loop.


								If C<do> cannot read the file, it returns undef and sets C<$!> to the

								error.  If C<do> can read the file but cannot compile it, it

								returns undef and sets an error message in C<$@>.   If the file is

								successfully compiled, C<do> returns the value of the last expression

								evaluated.


								Note that inclusion of library modules is better done with the

								C<use> and C<require> operators, which also do automatic error checking

								and raise an exception if there's a problem.


								You might like to use C<do> to read in a program configuration

								file.  Manual error checking can be done this way:


								    # read in config files: system first, then user

								    for $file ("/share/prog/defaults.rc",

								               "$ENV{HOME}/.someprogrc")

								   {

									unless ($return = do $file) {

									    warn "couldn't parse $file: $@" if $@;

									    warn "couldn't do $file: $!"    unless defined $return;

									    warn "couldn't run $file"       unless $return;

									}

								    }


								=item dump LABEL


								=item dump


								This function causes an immediate core dump.  See also the B<-u>

								command-line switch in L<perlrun>, which does the same thing.

								Primarily this is so that you can use the B<undump> program (not

								supplied) to turn your core dump into an executable binary after

								having initialized all your variables at the beginning of the

								program.  When the new binary is executed it will begin by executing

								a C<goto LABEL> (with all the restrictions that C<goto> suffers).

								Think of it as a goto with an intervening core dump and reincarnation.

								If C<LABEL> is omitted, restarts the program from the top.


								B<WARNING>: Any files opened at the time of the dump will I<not>

								be open any more when the program is reincarnated, with possible

								resulting confusion on the part of Perl.


								This function is now largely obsolete, partly because it's very

								hard to convert a core file into an executable, and because the

								real compiler backends for generating portable bytecode and compilable

								C code have superseded it.


								If you're looking to use L<dump> to speed up your program, consider

								generating bytecode or native C code as described in L<perlcc>.  If

								you're just trying to accelerate a CGI script, consider using the

								C<mod_perl> extension to B<Apache>, or the CPAN module, Fast::CGI.

								You might also consider autoloading or selfloading, which at least

								make your program I<appear> to run faster.


								=item each HASH


								When called in list context, returns a 2-element list consisting of the

								key and value for the next element of a hash, so that you can iterate over

								it.  When called in scalar context, returns only the key for the next

								element in the hash.


								Entries are returned in an apparently random order.  The actual random

								order is subject to change in future versions of perl, but it is guaranteed

								to be in the same order as either the C<keys> or C<values> function

								would produce on the same (unmodified) hash.


								When the hash is entirely read, a null array is returned in list context

								(which when assigned produces a false (C<0>) value), and C<undef> in

								scalar context.  The next call to C<each> after that will start iterating

								again.  There is a single iterator for each hash, shared by all C<each>,

								C<keys>, and C<values> function calls in the program; it can be reset by

								reading all the elements from the hash, or by evaluating C<keys HASH> or

								C<values HASH>.  If you add or delete elements of a hash while you're

								iterating over it, you may get entries skipped or duplicated, so

								don't.  Exception: It is always safe to delete the item most recently

								returned by C<each()>, which means that the following code will work:


								        while (($key, $value) = each %hash) {

								          print $key, "\n";

								          delete $hash{$key};   # This is safe

								        }


								The following prints out your environment like the printenv(1) program,

								only in a different order:


								    while (($key,$value) = each %ENV) {

									print "$key=$value\n";

								    }


								See also C<keys>, C<values> and C<sort>.


								=item eof FILEHANDLE


								=item eof ()


								=item eof


								Returns 1 if the next read on FILEHANDLE will return end of file, or if

								FILEHANDLE is not open.  FILEHANDLE may be an expression whose value

								gives the real filehandle.  (Note that this function actually

								reads a character and then C<ungetc>s it, so isn't very useful in an

								interactive context.)  Do not read from a terminal file (or call

								C<eof(FILEHANDLE)> on it) after end-of-file is reached.  File types such

								as terminals may lose the end-of-file condition if you do.


								An C<eof> without an argument uses the last file read.  Using C<eof()>

								with empty parentheses is very different.  It refers to the pseudo file

								formed from the files listed on the command line and accessed via the

								C<< <> >> operator.  Since C<< <> >> isn't explicitly opened,

								as a normal filehandle is, an C<eof()> before C<< <> >> has been

								used will cause C<@ARGV> to be examined to determine if input is

								available.


								In a C<< while (<>) >> loop, C<eof> or C<eof(ARGV)> can be used to

								detect the end of each file, C<eof()> will only detect the end of the

								last file.  Examples:


								    # reset line numbering on each input file

								    while (<>) {

									next if /^\s*#/;	# skip comments

									print "$.\t$_";

								    } continue {

									close ARGV  if eof;	# Not eof()!

								    }


								    # insert dashes just before last line of last file

								    while (<>) {

									if (eof()) {		# check for end of current file

									    print "--------------\n";

									    close(ARGV);	# close or last; is needed if we

												# are reading from the terminal

									}

									print;

								    }


								Practical hint: you almost never need to use C<eof> in Perl, because the

								input operators typically return C<undef> when they run out of data, or if

								there was an error.


								=item eval EXPR


								=item eval BLOCK


								In the first form, the return value of EXPR is parsed and executed as if it

								were a little Perl program.  The value of the expression (which is itself

								determined within scalar context) is first parsed, and if there weren't any

								errors, executed in the lexical context of the current Perl program, so

								that any variable settings or subroutine and format definitions remain

								afterwards.  Note that the value is parsed every time the eval executes.

								If EXPR is omitted, evaluates C<$_>.  This form is typically used to

								delay parsing and subsequent execution of the text of EXPR until run time.


								In the second form, the code within the BLOCK is parsed only once--at the

								same time the code surrounding the eval itself was parsed--and executed

								within the context of the current Perl program.  This form is typically

								used to trap exceptions more efficiently than the first (see below), while

								also providing the benefit of checking the code within BLOCK at compile

								time.


								The final semicolon, if any, may be omitted from the value of EXPR or within

								the BLOCK.


								In both forms, the value returned is the value of the last expression

								evaluated inside the mini-program; a return statement may be also used, just

								as with subroutines.  The expression providing the return value is evaluated

								in void, scalar, or list context, depending on the context of the eval itself.

								See L</wantarray> for more on how the evaluation context can be determined.


								If there is a syntax error or runtime error, or a C<die> statement is

								executed, an undefined value is returned by C<eval>, and C<$@> is set to the

								error message.  If there was no error, C<$@> is guaranteed to be a null

								string.  Beware that using C<eval> neither silences perl from printing

								warnings to STDERR, nor does it stuff the text of warning messages into C<$@>.

								To do either of those, you have to use the C<$SIG{__WARN__}> facility.  See

								L</warn> and L<perlvar>.


								Note that, because C<eval> traps otherwise-fatal errors, it is useful for

								determining whether a particular feature (such as C<socket> or C<symlink>)

								is implemented.  It is also Perl's exception trapping mechanism, where

								the die operator is used to raise exceptions.


								If the code to be executed doesn't vary, you may use the eval-BLOCK

								form to trap run-time errors without incurring the penalty of

								recompiling each time.  The error, if any, is still returned in C<$@>.

								Examples:


								    # make divide-by-zero nonfatal

								    eval { $answer = $a / $b; }; warn $@ if $@;


								    # same thing, but less efficient

								    eval '$answer = $a / $b'; warn $@ if $@;


								    # a compile-time error

								    eval { $answer = };			# WRONG


								    # a run-time error

								    eval '$answer =';	# sets $@


								Due to the current arguably broken state of C<__DIE__> hooks, when using

								the C<eval{}> form as an exception trap in libraries, you may wish not

								to trigger any C<__DIE__> hooks that user code may have installed.

								You can use the C<local $SIG{__DIE__}> construct for this purpose,

								as shown in this example:


								    # a very private exception trap for divide-by-zero

								    eval { local $SIG{'__DIE__'}; $answer = $a / $b; };

								    warn $@ if $@;


								This is especially significant, given that C<__DIE__> hooks can call

								C<die> again, which has the effect of changing their error messages:


								    # __DIE__ hooks may modify error messages

								    {

								       local $SIG{'__DIE__'} =

								              sub { (my $x = $_[0]) =~ s/foo/bar/g; die $x };

								       eval { die "foo lives here" };

								       print $@ if $@;                # prints "bar lives here"

								    }


								Because this promotes action at a distance, this counterintuitive behavior

								may be fixed in a future release.


								With an C<eval>, you should be especially careful to remember what's

								being looked at when:


								    eval $x;		# CASE 1

								    eval "$x";		# CASE 2


								    eval '$x';		# CASE 3

								    eval { $x };	# CASE 4


								    eval "\$$x++";	# CASE 5

								    $$x++;		# CASE 6


								Cases 1 and 2 above behave identically: they run the code contained in

								the variable $x.  (Although case 2 has misleading double quotes making

								the reader wonder what else might be happening (nothing is).)  Cases 3

								and 4 likewise behave in the same way: they run the code C<'$x'>, which

								does nothing but return the value of $x.  (Case 4 is preferred for

								purely visual reasons, but it also has the advantage of compiling at

								compile-time instead of at run-time.)  Case 5 is a place where

								normally you I<would> like to use double quotes, except that in this

								particular situation, you can just use symbolic references instead, as

								in case 6.


								C<eval BLOCK> does I<not> count as a loop, so the loop control statements

								C<next>, C<last>, or C<redo> cannot be used to leave or restart the block.


								=item exec LIST


								=item exec PROGRAM LIST


								The C<exec> function executes a system command I<and never returns>--

								use C<system> instead of C<exec> if you want it to return.  It fails and

								returns false only if the command does not exist I<and> it is executed

								directly instead of via your system's command shell (see below).


								Since it's a common mistake to use C<exec> instead of C<system>, Perl

								warns you if there is a following statement which isn't C<die>, C<warn>,

								or C<exit> (if C<-w> is set  -  but you always do that).   If you

								I<really> want to follow an C<exec> with some other statement, you

								can use one of these styles to avoid the warning:


								    exec ('foo')   or print STDERR "couldn't exec foo: $!";

								    { exec ('foo') }; print STDERR "couldn't exec foo: $!";


								If there is more than one argument in LIST, or if LIST is an array

								with more than one value, calls execvp(3) with the arguments in LIST.

								If there is only one scalar argument or an array with one element in it,

								the argument is checked for shell metacharacters, and if there are any,

								the entire argument is passed to the system's command shell for parsing

								(this is C</bin/sh -c> on Unix platforms, but varies on other platforms).

								If there are no shell metacharacters in the argument, it is split into

								words and passed directly to C<execvp>, which is more efficient.

								Examples:


								    exec '/bin/echo', 'Your arguments are: ', @ARGV;

								    exec "sort $outfile | uniq";


								If you don't really want to execute the first argument, but want to lie

								to the program you are executing about its own name, you can specify

								the program you actually want to run as an "indirect object" (without a

								comma) in front of the LIST.  (This always forces interpretation of the

								LIST as a multivalued list, even if there is only a single scalar in

								the list.)  Example:


								    $shell = '/bin/csh';

								    exec $shell '-sh';		# pretend it's a login shell


								or, more directly,


								    exec {'/bin/csh'} '-sh';	# pretend it's a login shell


								When the arguments get executed via the system shell, results will

								be subject to its quirks and capabilities.  See L<perlop/"`STRING`">

								for details.


								Using an indirect object with C<exec> or C<system> is also more

								secure.  This usage (which also works fine with system()) forces

								interpretation of the arguments as a multivalued list, even if the

								list had just one argument.  That way you're safe from the shell

								expanding wildcards or splitting up words with whitespace in them.


								    @args = ( "echo surprise" );


								    exec @args;               # subject to shell escapes

								                                # if @args == 1

								    exec { $args[0] } @args;  # safe even with one-arg list


								The first version, the one without the indirect object, ran the I<echo>

								program, passing it C<"surprise"> an argument.  The second version

								didn't--it tried to run a program literally called I<"echo surprise">,

								didn't find it, and set C<$?> to a non-zero value indicating failure.


								Beginning with v5.6.0, Perl will attempt to flush all files opened for

								output before the exec, but this may not be supported on some platforms

								(see L<perlport>).  To be safe, you may need to set C<$|> ($AUTOFLUSH

								in English) or call the C<autoflush()> method of C<IO::Handle> on any

								open handles in order to avoid lost output.


								Note that C<exec> will not call your C<END> blocks, nor will it call

								any C<DESTROY> methods in your objects.


								=item exists EXPR


								Given an expression that specifies a hash element or array element,

								returns true if the specified element in the hash or array has ever

								been initialized, even if the corresponding value is undefined.  The

								element is not autovivified if it doesn't exist.


								    print "Exists\n" 	if exists $hash{$key};

								    print "Defined\n" 	if defined $hash{$key};

								    print "True\n"      if $hash{$key};


								    print "Exists\n" 	if exists $array[$index];

								    print "Defined\n" 	if defined $array[$index];

								    print "True\n"      if $array[$index];


								A hash or array element can be true only if it's defined, and defined if

								it exists, but the reverse doesn't necessarily hold true.


								Given an expression that specifies the name of a subroutine,

								returns true if the specified subroutine has ever been declared, even

								if it is undefined.  Mentioning a subroutine name for exists or defined

								does not count as declaring it.  Note that a subroutine which does not

								exist may still be callable: its package may have an C<AUTOLOAD>

								method that makes it spring into existence the first time that it is

								called -- see L<perlsub>.


								    print "Exists\n" 	if exists &subroutine;

								    print "Defined\n" 	if defined &subroutine;


								Note that the EXPR can be arbitrarily complicated as long as the final

								operation is a hash or array key lookup or subroutine name:


								    if (exists $ref->{A}->{B}->{$key}) 	{ }

								    if (exists $hash{A}{B}{$key}) 	{ }


								    if (exists $ref->{A}->{B}->[$ix]) 	{ }

								    if (exists $hash{A}{B}[$ix]) 	{ }


								    if (exists &{$ref->{A}{B}{$key}})   { }


								Although the deepest nested array or hash will not spring into existence

								just because its existence was tested, any intervening ones will.

								Thus C<< $ref->{"A"} >> and C<< $ref->{"A"}->{"B"} >> will spring

								into existence due to the existence test for the $key element above.

								This happens anywhere the arrow operator is used, including even:


								    undef $ref;

								    if (exists $ref->{"Some key"})	{ }

								    print $ref; 	    # prints HASH(0x80d3d5c)


								This surprising autovivification in what does not at first--or even

								second--glance appear to be an lvalue context may be fixed in a future

								release.


								See L<perlref/"Pseudo-hashes: Using an array as a hash"> for specifics

								on how exists() acts when used on a pseudo-hash.


								Use of a subroutine call, rather than a subroutine name, as an argument

								to exists() is an error.


								    exists &sub;	# OK

								    exists &sub();	# Error


								=item exit EXPR


								Evaluates EXPR and exits immediately with that value.    Example:


								    $ans = <STDIN>;

								    exit 0 if $ans =~ /^[Xx]/;


								See also C<die>.  If EXPR is omitted, exits with C<0> status.  The only

								universally recognized values for EXPR are C<0> for success and C<1>

								for error; other values are subject to interpretation depending on the

								environment in which the Perl program is running.  For example, exiting

								69 (EX_UNAVAILABLE) from a I<sendmail> incoming-mail filter will cause

								the mailer to return the item undelivered, but that's not true everywhere.


								Don't use C<exit> to abort a subroutine if there's any chance that

								someone might want to trap whatever error happened.  Use C<die> instead,

								which can be trapped by an C<eval>.


								The exit() function does not always exit immediately.  It calls any

								defined C<END> routines first, but these C<END> routines may not

								themselves abort the exit.  Likewise any object destructors that need to

								be called are called before the real exit.  If this is a problem, you

								can call C<POSIX:_exit($status)> to avoid END and destructor processing.

								See L<perlmod> for details.


								=item exp EXPR


								=item exp


								Returns I<e> (the natural logarithm base) to the power of EXPR.

								If EXPR is omitted, gives C<exp($_)>.


								=item fcntl FILEHANDLE,FUNCTION,SCALAR


								Implements the fcntl(2) function.  You'll probably have to say


								    use Fcntl;


								first to get the correct constant definitions.  Argument processing and

								value return works just like C<ioctl> below.

								For example:


								    use Fcntl;

								    fcntl($filehandle, F_GETFL, $packed_return_buffer)

									or die "can't fcntl F_GETFL: $!";


								You don't have to check for C<defined> on the return from C<fnctl>.

								Like C<ioctl>, it maps a C<0> return from the system call into

								C<"0 but true"> in Perl.  This string is true in boolean context and C<0>

								in numeric context.  It is also exempt from the normal B<-w> warnings

								on improper numeric conversions.


								Note that C<fcntl> will produce a fatal error if used on a machine that

								doesn't implement fcntl(2).  See the Fcntl module or your fcntl(2)

								manpage to learn what functions are available on your system.


								=item fileno FILEHANDLE


								Returns the file descriptor for a filehandle, or undefined if the

								filehandle is not open.  This is mainly useful for constructing

								bitmaps for C<select> and low-level POSIX tty-handling operations.

								If FILEHANDLE is an expression, the value is taken as an indirect

								filehandle, generally its name.


								You can use this to find out whether two handles refer to the

								same underlying descriptor:


								    if (fileno(THIS) == fileno(THAT)) {

									print "THIS and THAT are dups\n";

								    }


								=item flock FILEHANDLE,OPERATION


								Calls flock(2), or an emulation of it, on FILEHANDLE.  Returns true

								for success, false on failure.  Produces a fatal error if used on a

								machine that doesn't implement flock(2), fcntl(2) locking, or lockf(3).

								C<flock> is Perl's portable file locking interface, although it locks

								only entire files, not records.


								Two potentially non-obvious but traditional C<flock> semantics are

								that it waits indefinitely until the lock is granted, and that its locks

								B<merely advisory>.  Such discretionary locks are more flexible, but offer

								fewer guarantees.  This means that files locked with C<flock> may be

								modified by programs that do not also use C<flock>.  See L<perlport>,

								your port's specific documentation, or your system-specific local manpages

								for details.  It's best to assume traditional behavior if you're writing

								portable programs.  (But if you're not, you should as always feel perfectly

								free to write for your own system's idiosyncrasies (sometimes called

								"features").  Slavish adherence to portability concerns shouldn't get

								in the way of your getting your job done.)


								OPERATION is one of LOCK_SH, LOCK_EX, or LOCK_UN, possibly combined with

								LOCK_NB.  These constants are traditionally valued 1, 2, 8 and 4, but

								you can use the symbolic names if you import them from the Fcntl module,

								either individually, or as a group using the ':flock' tag.  LOCK_SH

								requests a shared lock, LOCK_EX requests an exclusive lock, and LOCK_UN

								releases a previously requested lock.  If LOCK_NB is bitwise-or'ed with

								LOCK_SH or LOCK_EX then C<flock> will return immediately rather than blocking

								waiting for the lock (check the return status to see if you got it).


								To avoid the possibility of miscoordination, Perl now flushes FILEHANDLE

								before locking or unlocking it.


								Note that the emulation built with lockf(3) doesn't provide shared

								locks, and it requires that FILEHANDLE be open with write intent.  These

								are the semantics that lockf(3) implements.  Most if not all systems

								implement lockf(3) in terms of fcntl(2) locking, though, so the

								differing semantics shouldn't bite too many people.


								Note also that some versions of C<flock> cannot lock things over the

								network; you would need to use the more system-specific C<fcntl> for

								that.  If you like you can force Perl to ignore your system's flock(2)

								function, and so provide its own fcntl(2)-based emulation, by passing

								the switch C<-Ud_flock> to the F<Configure> program when you configure

								perl.


								Here's a mailbox appender for BSD systems.


								    use Fcntl ':flock'; # import LOCK_* constants


								    sub lock {

									flock(MBOX,LOCK_EX);

									# and, in case someone appended

									# while we were waiting...

									seek(MBOX, 0, 2);

								    }


								    sub unlock {

									flock(MBOX,LOCK_UN);

								    }


								    open(MBOX, ">>/usr/spool/mail/$ENV{'USER'}")

									    or die "Can't open mailbox: $!";


								    lock();

								    print MBOX $msg,"\n\n";

								    unlock();


								On systems that support a real flock(), locks are inherited across fork()

								calls, whereas those that must resort to the more capricious fcntl()

								function lose the locks, making it harder to write servers.


								See also L<DB_File> for other flock() examples.


								=item fork


								Does a fork(2) system call to create a new process running the

								same program at the same point.  It returns the child pid to the

								parent process, C<0> to the child process, or C<undef> if the fork is

								unsuccessful.  File descriptors (and sometimes locks on those descriptors)

								are shared, while everything else is copied.  On most systems supporting

								fork(), great care has gone into making it extremely efficient (for

								example, using copy-on-write technology on data pages), making it the

								dominant paradigm for multitasking over the last few decades.


								Beginning with v5.6.0, Perl will attempt to flush all files opened for

								output before forking the child process, but this may not be supported

								on some platforms (see L<perlport>).  To be safe, you may need to set

								C<$|> ($AUTOFLUSH in English) or call the C<autoflush()> method of

								C<IO::Handle> on any open handles in order to avoid duplicate output.


								If you C<fork> without ever waiting on your children, you will

								accumulate zombies.  On some systems, you can avoid this by setting

								C<$SIG{CHLD}> to C<"IGNORE">.  See also L<perlipc> for more examples of

								forking and reaping moribund children.


								Note that if your forked child inherits system file descriptors like

								STDIN and STDOUT that are actually connected by a pipe or socket, even

								if you exit, then the remote server (such as, say, a CGI script or a

								backgrounded job launched from a remote shell) won't think you're done.

								You should reopen those to F</dev/null> if it's any issue.


								=item format


								Declare a picture format for use by the C<write> function.  For

								example:


								    format Something =

									Test: @<<<<<<<< @||||| @>>>>>

									      $str,     $%,    '$' . int($num)

								    .


								    $str = "widget";

								    $num = $cost/$quantity;

								    $~ = 'Something';

								    write;


								See L<perlform> for many details and examples.


								=item formline PICTURE,LIST


								This is an internal function used by C<format>s, though you may call it,

								too.  It formats (see L<perlform>) a list of values according to the

								contents of PICTURE, placing the output into the format output

								accumulator, C<$^A> (or C<$ACCUMULATOR> in English).

								Eventually, when a C<write> is done, the contents of

								C<$^A> are written to some filehandle, but you could also read C<$^A>

								yourself and then set C<$^A> back to C<"">.  Note that a format typically

								does one C<formline> per line of form, but the C<formline> function itself

								doesn't care how many newlines are embedded in the PICTURE.  This means

								that the C<~> and C<~~> tokens will treat the entire PICTURE as a single line.

								You may therefore need to use multiple formlines to implement a single

								record format, just like the format compiler.


								Be careful if you put double quotes around the picture, because an C<@>

								character may be taken to mean the beginning of an array name.

								C<formline> always returns true.  See L<perlform> for other examples.


								=item getc FILEHANDLE


								=item getc


								Returns the next character from the input file attached to FILEHANDLE,

								or the undefined value at end of file, or if there was an error.

								If FILEHANDLE is omitted, reads from STDIN.  This is not particularly

								efficient.  However, it cannot be used by itself to fetch single

								characters without waiting for the user to hit enter.  For that, try

								something more like:


								    if ($BSD_STYLE) {

									system "stty cbreak </dev/tty >/dev/tty 2>&1";

								    }

								    else {

									system "stty", '-icanon', 'eol', "\001";

								    }


								    $key = getc(STDIN);


								    if ($BSD_STYLE) {

									system "stty -cbreak </dev/tty >/dev/tty 2>&1";

								    }

								    else {

									system "stty", 'icanon', 'eol', '^@'; # ASCII null

								    }

								    print "\n";


								Determination of whether $BSD_STYLE should be set

								is left as an exercise to the reader.


								The C<POSIX::getattr> function can do this more portably on

								systems purporting POSIX compliance.  See also the C<Term::ReadKey>

								module from your nearest CPAN site; details on CPAN can be found on

								L<perlmodlib/CPAN>.


								=item getlogin


								Implements the C library function of the same name, which on most

								systems returns the current login from F</etc/utmp>, if any.  If null,

								use C<getpwuid>.


								    $login = getlogin || getpwuid($<) || "Kilroy";


								Do not consider C<getlogin> for authentication: it is not as

								secure as C<getpwuid>.


								=item getpeername SOCKET


								Returns the packed sockaddr address of other end of the SOCKET connection.


								    use Socket;

								    $hersockaddr    = getpeername(SOCK);

								    ($port, $iaddr) = sockaddr_in($hersockaddr);

								    $herhostname    = gethostbyaddr($iaddr, AF_INET);

								    $herstraddr     = inet_ntoa($iaddr);


								=item getpgrp PID


								Returns the current process group for the specified PID.  Use

								a PID of C<0> to get the current process group for the

								current process.  Will raise an exception if used on a machine that

								doesn't implement getpgrp(2).  If PID is omitted, returns process

								group of current process.  Note that the POSIX version of C<getpgrp>

								does not accept a PID argument, so only C<PID==0> is truly portable.


								=item getppid


								Returns the process id of the parent process.


								=item getpriority WHICH,WHO


								Returns the current priority for a process, a process group, or a user.

								(See L<getpriority(2)>.)  Will raise a fatal exception if used on a

								machine that doesn't implement getpriority(2).


								=item getpwnam NAME


								=item getgrnam NAME


								=item gethostbyname NAME


								=item getnetbyname NAME


								=item getprotobyname NAME


								=item getpwuid UID


								=item getgrgid GID


								=item getservbyname NAME,PROTO


								=item gethostbyaddr ADDR,ADDRTYPE


								=item getnetbyaddr ADDR,ADDRTYPE


								=item getprotobynumber NUMBER


								=item getservbyport PORT,PROTO


								=item getpwent


								=item getgrent


								=item gethostent


								=item getnetent


								=item getprotoent


								=item getservent


								=item setpwent


								=item setgrent


								=item sethostent STAYOPEN


								=item setnetent STAYOPEN


								=item setprotoent STAYOPEN


								=item setservent STAYOPEN


								=item endpwent


								=item endgrent


								=item endhostent


								=item endnetent


								=item endprotoent


								=item endservent


								These routines perform the same functions as their counterparts in the

								system library.  In list context, the return values from the

								various get routines are as follows:


								    ($name,$passwd,$uid,$gid,

								       $quota,$comment,$gcos,$dir,$shell,$expire) = getpw*

								    ($name,$passwd,$gid,$members) = getgr*

								    ($name,$aliases,$addrtype,$length,@addrs) = gethost*

								    ($name,$aliases,$addrtype,$net) = getnet*

								    ($name,$aliases,$proto) = getproto*

								    ($name,$aliases,$port,$proto) = getserv*


								(If the entry doesn't exist you get a null list.)


								The exact meaning of the $gcos field varies but it usually contains

								the real name of the user (as opposed to the login name) and other

								information pertaining to the user.  Beware, however, that in many

								system users are able to change this information and therefore it

								cannot be trusted and therefore the $gcos is tainted (see

								L<perlsec>).  The $passwd and $shell, user's encrypted password and

								login shell, are also tainted, because of the same reason.


								In scalar context, you get the name, unless the function was a

								lookup by name, in which case you get the other thing, whatever it is.

								(If the entry doesn't exist you get the undefined value.)  For example:


								    $uid   = getpwnam($name);

								    $name  = getpwuid($num);

								    $name  = getpwent();

								    $gid   = getgrnam($name);

								    $name  = getgrgid($num;

								    $name  = getgrent();

								    #etc.


								In I<getpw*()> the fields $quota, $comment, and $expire are special

								cases in the sense that in many systems they are unsupported.  If the

								$quota is unsupported, it is an empty scalar.  If it is supported, it

								usually encodes the disk quota.  If the $comment field is unsupported,

								it is an empty scalar.  If it is supported it usually encodes some

								administrative comment about the user.  In some systems the $quota

								field may be $change or $age, fields that have to do with password

								aging.  In some systems the $comment field may be $class.  The $expire

								field, if present, encodes the expiration period of the account or the

								password.  For the availability and the exact meaning of these fields

								in your system, please consult your getpwnam(3) documentation and your

								F<pwd.h> file.  You can also find out from within Perl what your

								$quota and $comment fields mean and whether you have the $expire field

								by using the C<Config> module and the values C<d_pwquota>, C<d_pwage>,

								C<d_pwchange>, C<d_pwcomment>, and C<d_pwexpire>.  Shadow password

								files are only supported if your vendor has implemented them in the

								intuitive fashion that calling the regular C library routines gets the

								shadow versions if you're running under privilege or if there exists

								the shadow(3) functions as found in System V ( this includes Solaris

								and Linux.)  Those systems which implement a proprietary shadow password

								facility are unlikely to be supported.


								The $members value returned by I<getgr*()> is a space separated list of

								the login names of the members of the group.


								For the I<gethost*()> functions, if the C<h_errno> variable is supported in

								C, it will be returned to you via C<$?> if the function call fails.  The

								C<@addrs> value returned by a successful call is a list of the raw

								addresses returned by the corresponding system library call.  In the

								Internet domain, each address is four bytes long and you can unpack it

								by saying something like:


								    ($a,$b,$c,$d) = unpack('C4',$addr[0]);


								The Socket library makes this slightly easier:


								    use Socket;

								    $iaddr = inet_aton("127.1"); # or whatever address

								    $name  = gethostbyaddr($iaddr, AF_INET);


								    # or going the other way

								    $straddr = inet_ntoa($iaddr);


								If you get tired of remembering which element of the return list

								contains which return value, by-name interfaces are provided

								in standard modules: C<File::stat>, C<Net::hostent>, C<Net::netent>,

								C<Net::protoent>, C<Net::servent>, C<Time::gmtime>, C<Time::localtime>,

								and C<User::grent>.  These override the normal built-ins, supplying

								versions that return objects with the appropriate names

								for each field.  For example:


								   use File::stat;

								   use User::pwent;

								   $is_his = (stat($filename)->uid == pwent($whoever)->uid);


								Even though it looks like they're the same method calls (uid),

								they aren't, because a C<File::stat> object is different from

								a C<User::pwent> object.


								=item getsockname SOCKET


								Returns the packed sockaddr address of this end of the SOCKET connection,

								in case you don't know the address because you have several different

								IPs that the connection might have come in on.


								    use Socket;

								    $mysockaddr = getsockname(SOCK);

								    ($port, $myaddr) = sockaddr_in($mysockaddr);

								    printf "Connect to %s [%s]\n",

								       scalar gethostbyaddr($myaddr, AF_INET),

								       inet_ntoa($myaddr);


								=item getsockopt SOCKET,LEVEL,OPTNAME


								Returns the socket option requested, or undef if there is an error.


								=item glob EXPR


								=item glob


								Returns the value of EXPR with filename expansions such as the

								standard Unix shell F</bin/csh> would do.  This is the internal function

								implementing the C<< <*.c> >> operator, but you can use it directly.

								If EXPR is omitted, C<$_> is used.  The C<< <*.c> >> operator is

								discussed in more detail in L<perlop/"I/O Operators">.


								Beginning with v5.6.0, this operator is implemented using the standard

								C<File::Glob> extension.  See L<File::Glob> for details.


								=item gmtime EXPR


								Converts a time as returned by the time function to a 8-element list

								with the time localized for the standard Greenwich time zone.

								Typically used as follows:


								    #  0    1    2     3     4    5     6     7

								    ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday) =

													    gmtime(time);


								All list elements are numeric, and come straight out of the C `struct

								tm'.  $sec, $min, and $hour are the seconds, minutes, and hours of the

								specified time.  $mday is the day of the month, and $mon is the month

								itself, in the range C<0..11> with 0 indicating January and 11

								indicating December.  $year is the number of years since 1900.  That

								is, $year is C<123> in year 2023.  $wday is the day of the week, with

								0 indicating Sunday and 3 indicating Wednesday.  $yday is the day of

								the year, in the range C<0..364> (or C<0..365> in leap years.)


								Note that the $year element is I<not> simply the last two digits of

								the year.  If you assume it is, then you create non-Y2K-compliant

								programs--and you wouldn't want to do that, would you?


								The proper way to get a complete 4-digit year is simply:


									$year += 1900;


								And to get the last two digits of the year (e.g., '01' in 2001) do:


									$year = sprintf("%02d", $year % 100);


								If EXPR is omitted, C<gmtime()> uses the current time (C<gmtime(time)>).


								In scalar context, C<gmtime()> returns the ctime(3) value:


								    $now_string = gmtime;  # e.g., "Thu Oct 13 04:54:34 1994"


								Also see the C<timegm> function provided by the C<Time::Local> module,

								and the strftime(3) function available via the POSIX module.


								This scalar value is B<not> locale dependent (see L<perllocale>), but

								is instead a Perl builtin.  Also see the C<Time::Local> module, and the

								strftime(3) and mktime(3) functions available via the POSIX module.  To

								get somewhat similar but locale dependent date strings, set up your

								locale environment variables appropriately (please see L<perllocale>)

								and try for example:


								    use POSIX qw(strftime);

								    $now_string = strftime "%a %b %e %H:%M:%S %Y", gmtime;


								Note that the C<%a> and C<%b> escapes, which represent the short forms

								of the day of the week and the month of the year, may not necessarily

								be three characters wide in all locales.


								=item goto LABEL


								=item goto EXPR


								=item goto &NAME


								The C<goto-LABEL> form finds the statement labeled with LABEL and resumes

								execution there.  It may not be used to go into any construct that

								requires initialization, such as a subroutine or a C<foreach> loop.  It

								also can't be used to go into a construct that is optimized away,

								or to get out of a block or subroutine given to C<sort>.

								It can be used to go almost anywhere else within the dynamic scope,

								including out of subroutines, but it's usually better to use some other

								construct such as C<last> or C<die>.  The author of Perl has never felt the

								need to use this form of C<goto> (in Perl, that is--C is another matter).


								The C<goto-EXPR> form expects a label name, whose scope will be resolved

								dynamically.  This allows for computed C<goto>s per FORTRAN, but isn't

								necessarily recommended if you're optimizing for maintainability:


								    goto ("FOO", "BAR", "GLARCH")[$i];


								The C<goto-&NAME> form is quite different from the other forms of C<goto>.

								In fact, it isn't a goto in the normal sense at all, and doesn't have

								the stigma associated with other gotos.  Instead, it

								substitutes a call to the named subroutine for the currently running

								subroutine.  This is used by C<AUTOLOAD> subroutines that wish to load

								another subroutine and then pretend that the other subroutine had been

								called in the first place (except that any modifications to C<@_>

								in the current subroutine are propagated to the other subroutine.)

								After the C<goto>, not even C<caller> will be able to tell that this

								routine was called first.


								NAME needn't be the name of a subroutine; it can be a scalar variable

								containing a code reference, or a block which evaluates to a code

								reference.


								=item grep BLOCK LIST


								=item grep EXPR,LIST


								This is similar in spirit to, but not the same as, grep(1) and its

								relatives.  In particular, it is not limited to using regular expressions.


								Evaluates the BLOCK or EXPR for each element of LIST (locally setting

								C<$_> to each element) and returns the list value consisting of those

								elements for which the expression evaluated to true.  In scalar

								context, returns the number of times the expression was true.


								    @foo = grep(!/^#/, @bar);    # weed out comments


								or equivalently,


								    @foo = grep {!/^#/} @bar;    # weed out comments


								Note that C<$_> is an alias to the list value, so it can be used to

								modify the elements of the LIST.  While this is useful and supported,

								it can cause bizarre results if the elements of LIST are not variables.

								Similarly, grep returns aliases into the original list, much as a for

								loop's index variable aliases the list elements.  That is, modifying an

								element of a list returned by grep (for example, in a C<foreach>, C<map>

								or another C<grep>) actually modifies the element in the original list.

								This is usually something to be avoided when writing clear code.


								See also L</map> for a list composed of the results of the BLOCK or EXPR.


								=item hex EXPR


								=item hex


								Interprets EXPR as a hex string and returns the corresponding value.

								(To convert strings that might start with either 0, 0x, or 0b, see

								L</oct>.)  If EXPR is omitted, uses C<$_>.


								    print hex '0xAf'; # prints '175'

								    print hex 'aF';   # same


								Hex strings may only represent integers.  Strings that would cause

								integer overflow trigger a warning.


								=item import


								There is no builtin C<import> function.  It is just an ordinary

								method (subroutine) defined (or inherited) by modules that wish to export

								names to another module.  The C<use> function calls the C<import> method

								for the package used.  See also L</use>, L<perlmod>, and L<Exporter>.


								=item index STR,SUBSTR,POSITION


								=item index STR,SUBSTR


								The index function searches for one string within another, but without

								the wildcard-like behavior of a full regular-expression pattern match.

								It returns the position of the first occurrence of SUBSTR in STR at

								or after POSITION.  If POSITION is omitted, starts searching from the

								beginning of the string.  The return value is based at C<0> (or whatever

								you've set the C<$[> variable to--but don't do that).  If the substring

								is not found, returns one less than the base, ordinarily C<-1>.


								=item int EXPR


								=item int


								Returns the integer portion of EXPR.  If EXPR is omitted, uses C<$_>.

								You should not use this function for rounding: one because it truncates

								towards C<0>, and two because machine representations of floating point

								numbers can sometimes produce counterintuitive results.  For example,

								C<int(-6.725/0.025)> produces -268 rather than the correct -269; that's

								because it's really more like -268.99999999999994315658 instead.  Usually,

								the C<sprintf>, C<printf>, or the C<POSIX::floor> and C<POSIX::ceil>

								functions will serve you better than will int().


								=item ioctl FILEHANDLE,FUNCTION,SCALAR


								Implements the ioctl(2) function.  You'll probably first have to say


								    require "ioctl.ph";	# probably in /usr/local/lib/perl/ioctl.ph


								to get the correct function definitions.  If F<ioctl.ph> doesn't

								exist or doesn't have the correct definitions you'll have to roll your

								own, based on your C header files such as F<< <sys/ioctl.h> >>.

								(There is a Perl script called B<h2ph> that comes with the Perl kit that

								may help you in this, but it's nontrivial.)  SCALAR will be read and/or

								written depending on the FUNCTION--a pointer to the string value of SCALAR

								will be passed as the third argument of the actual C<ioctl> call.  (If SCALAR

								has no string value but does have a numeric value, that value will be

								passed rather than a pointer to the string value.  To guarantee this to be

								true, add a C<0> to the scalar before using it.)  The C<pack> and C<unpack>

								functions may be needed to manipulate the values of structures used by

								C<ioctl>.


								The return value of C<ioctl> (and C<fcntl>) is as follows:


									if OS returns:		then Perl returns:

									    -1	  		  undefined value

									     0	 		string "0 but true"

									anything else		    that number


								Thus Perl returns true on success and false on failure, yet you can

								still easily determine the actual value returned by the operating

								system:


								    $retval = ioctl(...) || -1;

								    printf "System returned %d\n", $retval;


								The special string "C<0> but true" is exempt from B<-w> complaints

								about improper numeric conversions.


								Here's an example of setting a filehandle named C<REMOTE> to be

								non-blocking at the system level.  You'll have to negotiate C<$|>

								on your own, though.


								    use Fcntl qw(F_GETFL F_SETFL O_NONBLOCK);


								    $flags = fcntl(REMOTE, F_GETFL, 0)

								                or die "Can't get flags for the socket: $!\n";


								    $flags = fcntl(REMOTE, F_SETFL, $flags | O_NONBLOCK)

								                or die "Can't set flags for the socket: $!\n";


								=item join EXPR,LIST


								Joins the separate strings of LIST into a single string with fields

								separated by the value of EXPR, and returns that new string.  Example:


								    $rec = join(':', $login,$passwd,$uid,$gid,$gcos,$home,$shell);


								Beware that unlike C<split>, C<join> doesn't take a pattern as its

								first argument.  Compare L</split>.


								=item keys HASH


								Returns a list consisting of all the keys of the named hash.  (In

								scalar context, returns the number of keys.)  The keys are returned in

								an apparently random order.  The actual random order is subject to

								change in future versions of perl, but it is guaranteed to be the same

								order as either the C<values> or C<each> function produces (given

								that the hash has not been modified).  As a side effect, it resets

								HASH's iterator.


								Here is yet another way to print your environment:


								    @keys = keys %ENV;

								    @values = values %ENV;

								    while (@keys) {

									print pop(@keys), '=', pop(@values), "\n";

								    }


								or how about sorted by key:


								    foreach $key (sort(keys %ENV)) {

									print $key, '=', $ENV{$key}, "\n";

								    }


								The returned values are copies of the original keys in the hash, so

								modifying them will not affect the original hash.  Compare L</values>.


								To sort a hash by value, you'll need to use a C<sort> function.

								Here's a descending numeric sort of a hash by its values:


								    foreach $key (sort { $hash{$b} <=> $hash{$a} } keys %hash) {

									printf "%4d %s\n", $hash{$key}, $key;

								    }


								As an lvalue C<keys> allows you to increase the number of hash buckets

								allocated for the given hash.  This can gain you a measure of efficiency if

								you know the hash is going to get big.  (This is similar to pre-extending

								an array by assigning a larger number to $#array.)  If you say


								    keys %hash = 200;


								then C<%hash> will have at least 200 buckets allocated for it--256 of them,

								in fact, since it rounds up to the next power of two.  These

								buckets will be retained even if you do C<%hash = ()>, use C<undef

								%hash> if you want to free the storage while C<%hash> is still in scope.

								You can't shrink the number of buckets allocated for the hash using

								C<keys> in this way (but you needn't worry about doing this by accident,

								as trying has no effect).


								See also C<each>, C<values> and C<sort>.


								=item kill SIGNAL, LIST


								Sends a signal to a list of processes.  Returns the number of

								processes successfully signaled (which is not necessarily the

								same as the number actually killed).


								    $cnt = kill 1, $child1, $child2;

								    kill 9, @goners;


								If SIGNAL is zero, no signal is sent to the process.  This is a

								useful way to check that the process is alive and hasn't changed

								its UID.  See L<perlport> for notes on the portability of this

								construct.


								Unlike in the shell, if SIGNAL is negative, it kills

								process groups instead of processes.  (On System V, a negative I<PROCESS>

								number will also kill process groups, but that's not portable.)  That

								means you usually want to use positive not negative signals.  You may also

								use a signal name in quotes.  See L<perlipc/"Signals"> for details.


								=item last LABEL


								=item last


								The C<last> command is like the C<break> statement in C (as used in

								loops); it immediately exits the loop in question.  If the LABEL is

								omitted, the command refers to the innermost enclosing loop.  The

								C<continue> block, if any, is not executed:


								    LINE: while (<STDIN>) {

									last LINE if /^$/;	# exit when done with header

									#...

								    }


								C<last> cannot be used to exit a block which returns a value such as

								C<eval {}>, C<sub {}> or C<do {}>, and should not be used to exit

								a grep() or map() operation.


								Note that a block by itself is semantically identical to a loop

								that executes once.  Thus C<last> can be used to effect an early

								exit out of such a block.


								See also L</continue> for an illustration of how C<last>, C<next>, and

								C<redo> work.


								=item lc EXPR


								=item lc


								Returns an lowercased version of EXPR.  This is the internal function

								implementing the C<\L> escape in double-quoted strings.

								Respects current LC_CTYPE locale if C<use locale> in force.  See L<perllocale>

								and L<utf8>.


								If EXPR is omitted, uses C<$_>.


								=item lcfirst EXPR


								=item lcfirst


								Returns the value of EXPR with the first character lowercased.  This is

								the internal function implementing the C<\l> escape in double-quoted strings.

								Respects current LC_CTYPE locale if C<use locale> in force.  See L<perllocale>.


								If EXPR is omitted, uses C<$_>.


								=item length EXPR


								=item length


								Returns the length in characters of the value of EXPR.  If EXPR is

								omitted, returns length of C<$_>.  Note that this cannot be used on

								an entire array or hash to find out how many elements these have.

								For that, use C<scalar @array> and C<scalar keys %hash> respectively.


								=item link OLDFILE,NEWFILE


								Creates a new filename linked to the old filename.  Returns true for

								success, false otherwise.


								=item listen SOCKET,QUEUESIZE


								Does the same thing that the listen system call does.  Returns true if

								it succeeded, false otherwise.  See the example in

								L<perlipc/"Sockets: Client/Server Communication">.


								=item local EXPR


								You really probably want to be using C<my> instead, because C<local> isn't

								what most people think of as "local".  See

								L<perlsub/"Private Variables via my()"> for details.


								A local modifies the listed variables to be local to the enclosing

								block, file, or eval.  If more than one value is listed, the list must

								be placed in parentheses.  See L<perlsub/"Temporary Values via local()">

								for details, including issues with tied arrays and hashes.


								=item localtime EXPR


								Converts a time as returned by the time function to a 9-element list

								with the time analyzed for the local time zone.  Typically used as

								follows:


								    #  0    1    2     3     4    5     6     7     8

								    ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =

														localtime(time);


								All list elements are numeric, and come straight out of the C `struct

								tm'.  $sec, $min, and $hour are the seconds, minutes, and hours of the

								specified time.  $mday is the day of the month, and $mon is the month

								itself, in the range C<0..11> with 0 indicating January and 11

								indicating December.  $year is the number of years since 1900.  That

								is, $year is C<123> in year 2023.  $wday is the day of the week, with

								0 indicating Sunday and 3 indicating Wednesday.  $yday is the day of

								the year, in the range C<0..364> (or C<0..365> in leap years.)  $isdst

								is true if the specified time occurs during daylight savings time,

								false otherwise.


								Note that the $year element is I<not> simply the last two digits of

								the year.  If you assume it is, then you create non-Y2K-compliant

								programs--and you wouldn't want to do that, would you?


								The proper way to get a complete 4-digit year is simply:


									$year += 1900;


								And to get the last two digits of the year (e.g., '01' in 2001) do:


									$year = sprintf("%02d", $year % 100);


								If EXPR is omitted, C<localtime()> uses the current time (C<localtime(time)>).


								In scalar context, C<localtime()> returns the ctime(3) value:


								    $now_string = localtime;  # e.g., "Thu Oct 13 04:54:34 1994"


								This scalar value is B<not> locale dependent, see L<perllocale>, but

								instead a Perl builtin.  Also see the C<Time::Local> module

								(to convert the second, minutes, hours, ... back to seconds since the

								stroke of midnight the 1st of January 1970, the value returned by

								time()), and the strftime(3) and mktime(3) functions available via the

								POSIX module.  To get somewhat similar but locale dependent date

								strings, set up your locale environment variables appropriately

								(please see L<perllocale>) and try for example:


								    use POSIX qw(strftime);

								    $now_string = strftime "%a %b %e %H:%M:%S %Y", localtime;


								Note that the C<%a> and C<%b>, the short forms of the day of the week

								and the month of the year, may not necessarily be three characters wide.


								=item lock


								    lock I<THING>


								This function places an advisory lock on a variable, subroutine,

								or referenced object contained in I<THING> until the lock goes out

								of scope.  This is a built-in function only if your version of Perl

								was built with threading enabled, and if you've said C<use Threads>.

								Otherwise a user-defined function by this name will be called.  See

								L<Thread>.


								=item log EXPR


								=item log


								Returns the natural logarithm (base I<e>) of EXPR.  If EXPR is omitted,

								returns log of C<$_>.  To get the log of another base, use basic algebra:

								The base-N log of a number is equal to the natural log of that number

								divided by the natural log of N.  For example:


								    sub log10 {

									my $n = shift;

									return log($n)/log(10);

								    }


								See also L</exp> for the inverse operation.


								=item lstat FILEHANDLE


								=item lstat EXPR


								=item lstat


								Does the same thing as the C<stat> function (including setting the

								special C<_> filehandle) but stats a symbolic link instead of the file

								the symbolic link points to.  If symbolic links are unimplemented on

								your system, a normal C<stat> is done.


								If EXPR is omitted, stats C<$_>.


								=item m//


								The match operator.  See L<perlop>.


								=item map BLOCK LIST


								=item map EXPR,LIST


								Evaluates the BLOCK or EXPR for each element of LIST (locally setting

								C<$_> to each element) and returns the list value composed of the

								results of each such evaluation.  In scalar context, returns the

								total number of elements so generated.  Evaluates BLOCK or EXPR in

								list context, so each element of LIST may produce zero, one, or

								more elements in the returned value.


								    @chars = map(chr, @nums);


								translates a list of numbers to the corresponding characters.  And


								    %hash = map { getkey($_) => $_ } @array;


								is just a funny way to write


								    %hash = ();

								    foreach $_ (@array) {

									$hash{getkey($_)} = $_;

								    }


								Note that C<$_> is an alias to the list value, so it can be used to

								modify the elements of the LIST.  While this is useful and supported,

								it can cause bizarre results if the elements of LIST are not variables.

								Using a regular C<foreach> loop for this purpose would be clearer in

								most cases.  See also L</grep> for an array composed of those items of

								the original list for which the BLOCK or EXPR evaluates to true.


								C<{> starts both hash references and blocks, so C<map { ...> could be either

								the start of map BLOCK LIST or map EXPR, LIST. Because perl doesn't look

								ahead for the closing C<}> it has to take a guess at which its dealing with

								based what it finds just after the C<{>. Usually it gets it right, but if it

								doesn't it won't realize something is wrong until it gets to the C<}> and

								encounters the missing (or unexpected) comma. The syntax error will be

								reported close to the C<}> but you'll need to change something near the C<{>

								such as using a unary C<+> to give perl some help:


								    %hash = map {  "\L$_", 1  } @array  # perl guesses EXPR.  wrong

								    %hash = map { +"\L$_", 1  } @array  # perl guesses BLOCK. right

								    %hash = map { ("\L$_", 1) } @array  # this also works

								    %hash = map {  lc($_), 1  } @array  # as does this.

								    %hash = map +( lc($_), 1 ), @array  # this is EXPR and works!


								    %hash = map  ( lc($_), 1 ), @array  # evaluates to (1, @array)


								or to force an anon hash constructor use C<+{>


								   @hashes = map +{ lc($_), 1 }, @array # EXPR, so needs , at end


								and you get list of anonymous hashes each with only 1 entry.


								=item mkdir FILENAME,MASK


								=item mkdir FILENAME


								Creates the directory specified by FILENAME, with permissions

								specified by MASK (as modified by C<umask>).  If it succeeds it

								returns true, otherwise it returns false and sets C<$!> (errno).

								If omitted, MASK defaults to 0777.


								In general, it is better to create directories with permissive MASK,

								and let the user modify that with their C<umask>, than it is to supply

								a restrictive MASK and give the user no way to be more permissive.

								The exceptions to this rule are when the file or directory should be

								kept private (mail files, for instance).  The perlfunc(1) entry on

								C<umask> discusses the choice of MASK in more detail.


								=item msgctl ID,CMD,ARG


								Calls the System V IPC function msgctl(2).  You'll probably have to say


								    use IPC::SysV;


								first to get the correct constant definitions.  If CMD is C<IPC_STAT>,

								then ARG must be a variable which will hold the returned C<msqid_ds>

								structure.  Returns like C<ioctl>: the undefined value for error,

								C<"0 but true"> for zero, or the actual return value otherwise.  See also

								L<perlipc/"SysV IPC">, C<IPC::SysV>, and C<IPC::Semaphore> documentation.


								=item msgget KEY,FLAGS


								Calls the System V IPC function msgget(2).  Returns the message queue

								id, or the undefined value if there is an error.  See also

								L<perlipc/"SysV IPC"> and C<IPC::SysV> and C<IPC::Msg> documentation.


								=item msgrcv ID,VAR,SIZE,TYPE,FLAGS


								Calls the System V IPC function msgrcv to receive a message from

								message queue ID into variable VAR with a maximum message size of

								SIZE.  Note that when a message is received, the message type as a

								native long integer will be the first thing in VAR, followed by the

								actual message.  This packing may be opened with C<unpack("l! a*")>.

								Taints the variable.  Returns true if successful, or false if there is

								an error.  See also L<perlipc/"SysV IPC">, C<IPC::SysV>, and

								C<IPC::SysV::Msg> documentation.


								=item msgsnd ID,MSG,FLAGS


								Calls the System V IPC function msgsnd to send the message MSG to the

								message queue ID.  MSG must begin with the native long integer message

								type, and be followed by the length of the actual message, and finally

								the message itself.  This kind of packing can be achieved with

								C<pack("l! a*", $type, $message)>.  Returns true if successful,

								or false if there is an error.  See also C<IPC::SysV>

								and C<IPC::SysV::Msg> documentation.


								=item my EXPR


								=item my EXPR : ATTRIBUTES


								A C<my> declares the listed variables to be local (lexically) to the

								enclosing block, file, or C<eval>.  If

								more than one value is listed, the list must be placed in parentheses.  See

								L<perlsub/"Private Variables via my()"> for details.


								=item next LABEL


								=item next


								The C<next> command is like the C<continue> statement in C; it starts

								the next iteration of the loop:


								    LINE: while (<STDIN>) {

									next LINE if /^#/;	# discard comments

									#...

								    }


								Note that if there were a C<continue> block on the above, it would get

								executed even on discarded lines.  If the LABEL is omitted, the command

								refers to the innermost enclosing loop.


								C<next> cannot be used to exit a block which returns a value such as

								C<eval {}>, C<sub {}> or C<do {}>, and should not be used to exit

								a grep() or map() operation.


								Note that a block by itself is semantically identical to a loop

								that executes once.  Thus C<next> will exit such a block early.


								See also L</continue> for an illustration of how C<last>, C<next>, and

								C<redo> work.


								=item no Module LIST


								See the L</use> function, which C<no> is the opposite of.


								=item oct EXPR


								=item oct


								Interprets EXPR as an octal string and returns the corresponding

								value.  (If EXPR happens to start off with C<0x>, interprets it as a

								hex string.  If EXPR starts off with C<0b>, it is interpreted as a

								binary string.)  The following will handle decimal, binary, octal, and

								hex in the standard Perl or C notation:


								    $val = oct($val) if $val =~ /^0/;


								If EXPR is omitted, uses C<$_>.   To go the other way (produce a number

								in octal), use sprintf() or printf():


								    $perms = (stat("filename"))[2] & 07777;

								    $oct_perms = sprintf "%lo", $perms;


								The oct() function is commonly used when a string such as C<644> needs

								to be converted into a file mode, for example. (Although perl will

								automatically convert strings into numbers as needed, this automatic

								conversion assumes base 10.)


								=item open FILEHANDLE,MODE,LIST


								=item open FILEHANDLE,EXPR


								=item open FILEHANDLE


								Opens the file whose filename is given by EXPR, and associates it with

								FILEHANDLE.  If FILEHANDLE is an expression, its value is used as the

								name of the real filehandle wanted.  (This is considered a symbolic

								reference, so C<use strict 'refs'> should I<not> be in effect.)


								If EXPR is omitted, the scalar

								variable of the same name as the FILEHANDLE contains the filename.

								(Note that lexical variables--those declared with C<my>--will not work

								for this purpose; so if you're using C<my>, specify EXPR in your call

								to open.)  See L<perlopentut> for a kinder, gentler explanation of opening

								files.


								If MODE is C<< '<' >> or nothing, the file is opened for input.

								If MODE is C<< '>' >>, the file is truncated and opened for

								output, being created if necessary.  If MODE is C<<< '>>' >>>,

								the file is opened for appending, again being created if necessary.

								You can put a C<'+'> in front of the C<< '>' >> or C<< '<' >> to indicate that

								you want both read and write access to the file; thus C<< '+<' >> is almost

								always preferred for read/write updates--the C<< '+>' >> mode would clobber the

								file first.  You can't usually use either read-write mode for updating

								textfiles, since they have variable length records.  See the B<-i>

								switch in L<perlrun> for a better approach.  The file is created with

								permissions of C<0666> modified by the process' C<umask> value.


								These various prefixes correspond to the fopen(3) modes of C<'r'>, C<'r+'>,

								C<'w'>, C<'w+'>, C<'a'>, and C<'a+'>.


								In the 2-arguments (and 1-argument) form of the call the mode and

								filename should be concatenated (in this order), possibly separated by

								spaces.  It is possible to omit the mode if the mode is C<< '<' >>.


								If the filename begins with C<'|'>, the filename is interpreted as a

								command to which output is to be piped, and if the filename ends with a

								C<'|'>, the filename is interpreted as a command which pipes output to

								us.  See L<perlipc/"Using open() for IPC">

								for more examples of this.  (You are not allowed to C<open> to a command

								that pipes both in I<and> out, but see L<IPC::Open2>, L<IPC::Open3>,

								and L<perlipc/"Bidirectional Communication with Another Process">

								for alternatives.)


								If MODE is C<'|-'>, the filename is interpreted as a

								command to which output is to be piped, and if MODE is

								C<'-|'>, the filename is interpreted as a command which pipes output to

								us.  In the 2-arguments (and 1-argument) form one should replace dash

								(C<'-'>) with the command.  See L<perlipc/"Using open() for IPC">

								for more examples of this.  (You are not allowed to C<open> to a command

								that pipes both in I<and> out, but see L<IPC::Open2>, L<IPC::Open3>,

								and L<perlipc/"Bidirectional Communication"> for alternatives.)


								In the 2-arguments (and 1-argument) form opening C<'-'> opens STDIN

								and opening C<< '>-' >> opens STDOUT.


								Open returns

								nonzero upon success, the undefined value otherwise.  If the C<open>

								involved a pipe, the return value happens to be the pid of the

								subprocess.


								If you're unfortunate enough to be running Perl on a system that

								distinguishes between text files and binary files (modern operating

								systems don't care), then you should check out L</binmode> for tips for

								dealing with this.  The key distinction between systems that need C<binmode>

								and those that don't is their text file formats.  Systems like Unix, MacOS, and

								Plan9, which delimit lines with a single character, and which encode that

								character in C as C<"\n">, do not need C<binmode>.  The rest need it.


								When opening a file, it's usually a bad idea to continue normal execution

								if the request failed, so C<open> is frequently used in connection with

								C<die>.  Even if C<die> won't do what you want (say, in a CGI script,

								where you want to make a nicely formatted error message (but there are

								modules that can help with that problem)) you should always check

								the return value from opening a file.  The infrequent exception is when

								working with an unopened filehandle is actually what you want to do.


								Examples:


								    $ARTICLE = 100;

								    open ARTICLE or die "Can't find article $ARTICLE: $!\n";

								    while (<ARTICLE>) {...


								    open(LOG, '>>/usr/spool/news/twitlog');	# (log is reserved)

								    # if the open fails, output is discarded


								    open(DBASE, '+<', 'dbase.mine')		# open for update

									or die "Can't open 'dbase.mine' for update: $!";


								    open(DBASE, '+<dbase.mine')			# ditto

									or die "Can't open 'dbase.mine' for update: $!";


								    open(ARTICLE, '-|', "caesar <$article")     # decrypt article

									or die "Can't start caesar: $!";


								    open(ARTICLE, "caesar <$article |")		# ditto

									or die "Can't start caesar: $!";


								    open(EXTRACT, "|sort >/tmp/Tmp$$")		# $$ is our process id

									or die "Can't start sort: $!";


								    # process argument list of files along with any includes


								    foreach $file (@ARGV) {

									process($file, 'fh00');

								    }


								    sub process {

									my($filename, $input) = @_;

									$input++;		# this is a string increment

									unless (open($input, $filename)) {

									    print STDERR "Can't open $filename: $!\n";

									    return;

									}


									local $_;

									while (<$input>) {		# note use of indirection

									    if (/^#include "(.*)"/) {

										process($1, $input);

										next;

									    }

									    #...		# whatever

									}

								    }


								You may also, in the Bourne shell tradition, specify an EXPR beginning

								with C<< '>&' >>, in which case the rest of the string is interpreted as the

								name of a filehandle (or file descriptor, if numeric) to be

								duped and opened.  You may use C<&> after C<< > >>, C<<< >> >>>,

								C<< < >>, C<< +> >>, C<<< +>> >>>, and C<< +< >>.  The

								mode you specify should match the mode of the original filehandle.

								(Duping a filehandle does not take into account any existing contents of

								stdio buffers.)  Duping file handles is not yet supported for 3-argument

								open().


								Here is a script that saves, redirects, and restores STDOUT and

								STDERR:


								    #!/usr/bin/perl

								    open(OLDOUT, ">&STDOUT");

								    open(OLDERR, ">&STDERR");


								    open(STDOUT, '>', "foo.out") || die "Can't redirect stdout";

								    open(STDERR, ">&STDOUT")     || die "Can't dup stdout";


								    select(STDERR); $| = 1;	# make unbuffered

								    select(STDOUT); $| = 1;	# make unbuffered


								    print STDOUT "stdout 1\n";	# this works for

								    print STDERR "stderr 1\n"; 	# subprocesses too


								    close(STDOUT);

								    close(STDERR);


								    open(STDOUT, ">&OLDOUT");

								    open(STDERR, ">&OLDERR");


								    print STDOUT "stdout 2\n";

								    print STDERR "stderr 2\n";


								If you specify C<< '<&=N' >>, where C<N> is a number, then Perl will do an

								equivalent of C's C<fdopen> of that file descriptor; this is more

								parsimonious of file descriptors.  For example:


								    open(FILEHANDLE, "<&=$fd")


								Note that this feature depends on the fdopen() C library function.

								On many UNIX systems, fdopen() is known to fail when file descriptors

								exceed a certain value, typically 255. If you need more file

								descriptors than that, consider rebuilding Perl to use the C<sfio>

								library.


								If you open a pipe on the command C<'-'>, i.e., either C<'|-'> or C<'-|'>

								with 2-arguments (or 1-argument) form of open(), then

								there is an implicit fork done, and the return value of open is the pid

								of the child within the parent process, and C<0> within the child

								process.  (Use C<defined($pid)> to determine whether the open was successful.)

								The filehandle behaves normally for the parent, but i/o to that

								filehandle is piped from/to the STDOUT/STDIN of the child process.

								In the child process the filehandle isn't opened--i/o happens from/to

								the new STDOUT or STDIN.  Typically this is used like the normal

								piped open when you want to exercise more control over just how the

								pipe command gets executed, such as when you are running setuid, and

								don't want to have to scan shell commands for metacharacters.

								The following triples are more or less equivalent:


								    open(FOO, "|tr '[a-z]' '[A-Z]'");

								    open(FOO, '|-', "tr '[a-z]' '[A-Z]'");

								    open(FOO, '|-') || exec 'tr', '[a-z]', '[A-Z]';


								    open(FOO, "cat -n '$file'|");

								    open(FOO, '-|', "cat -n '$file'");

								    open(FOO, '-|') || exec 'cat', '-n', $file;


								See L<perlipc/"Safe Pipe Opens"> for more examples of this.


								Beginning with v5.6.0, Perl will attempt to flush all files opened for

								output before any operation that may do a fork, but this may not be

								supported on some platforms (see L<perlport>).  To be safe, you may need

								to set C<$|> ($AUTOFLUSH in English) or call the C<autoflush()> method

								of C<IO::Handle> on any open handles.


								On systems that support a

								close-on-exec flag on files, the flag will be set for the newly opened

								file descriptor as determined by the value of $^F.  See L<perlvar/$^F>.


								Closing any piped filehandle causes the parent process to wait for the

								child to finish, and returns the status value in C<$?>.


								The filename passed to 2-argument (or 1-argument) form of open()

								will have leading and trailing

								whitespace deleted, and the normal redirection characters

								honored.  This property, known as "magic open",

								can often be used to good effect.  A user could specify a filename of

								F<"rsh cat file |">, or you could change certain filenames as needed:


								    $filename =~ s/(.*\.gz)\s*$/gzip -dc < $1|/;

								    open(FH, $filename) or die "Can't open $filename: $!";


								Use 3-argument form to open a file with arbitrary weird characters in it,


								    open(FOO, '<', $file);


								otherwise it's necessary to protect any leading and trailing whitespace:


								    $file =~ s#^(\s)#./$1#;

								    open(FOO, "< $file\0");


								(this may not work on some bizarre filesystems).  One should

								conscientiously choose between the I<magic> and 3-arguments form

								of open():


								    open IN, $ARGV[0];


								will allow the user to specify an argument of the form C<"rsh cat file |">,

								but will not work on a filename which happens to have a trailing space, while


								    open IN, '<', $ARGV[0];


								will have exactly the opposite restrictions.


								If you want a "real" C C<open> (see L<open(2)> on your system), then you

								should use the C<sysopen> function, which involves no such magic (but

								may use subtly different filemodes than Perl open(), which is mapped

								to C fopen()).  This is

								another way to protect your filenames from interpretation.  For example:


								    use IO::Handle;

								    sysopen(HANDLE, $path, O_RDWR|O_CREAT|O_EXCL)

									or die "sysopen $path: $!";

								    $oldfh = select(HANDLE); $| = 1; select($oldfh);

								    print HANDLE "stuff $$\n";

								    seek(HANDLE, 0, 0);

								    print "File contains: ", <HANDLE>;


								Using the constructor from the C<IO::Handle> package (or one of its

								subclasses, such as C<IO::File> or C<IO::Socket>), you can generate anonymous

								filehandles that have the scope of whatever variables hold references to

								them, and automatically close whenever and however you leave that scope:


								    use IO::File;

								    #...

								    sub read_myfile_munged {

									my $ALL = shift;

									my $handle = new IO::File;

									open($handle, "myfile") or die "myfile: $!";

									$first = <$handle>

									    or return ();     # Automatically closed here.

									mung $first or die "mung failed";	# Or here.

									return $first, <$handle> if $ALL;	# Or here.

									$first;					# Or here.

								    }


								See L</seek> for some details about mixing reading and writing.


								=item opendir DIRHANDLE,EXPR


								Opens a directory named EXPR for processing by C<readdir>, C<telldir>,

								C<seekdir>, C<rewinddir>, and C<closedir>.  Returns true if successful.

								DIRHANDLEs have their own namespace separate from FILEHANDLEs.


								=item ord EXPR


								=item ord


								Returns the numeric (ASCII or Unicode) value of the first character of EXPR.  If

								EXPR is omitted, uses C<$_>.  For the reverse, see L</chr>.

								See L<utf8> for more about Unicode.


								=item our EXPR


								An C<our> declares the listed variables to be valid globals within

								the enclosing block, file, or C<eval>.  That is, it has the same

								scoping rules as a "my" declaration, but does not create a local

								variable.  If more than one value is listed, the list must be placed

								in parentheses.  The C<our> declaration has no semantic effect unless

								"use strict vars" is in effect, in which case it lets you use the

								declared global variable without qualifying it with a package name.

								(But only within the lexical scope of the C<our> declaration.  In this

								it differs from "use vars", which is package scoped.)


								An C<our> declaration declares a global variable that will be visible

								across its entire lexical scope, even across package boundaries.  The

								package in which the variable is entered is determined at the point

								of the declaration, not at the point of use.  This means the following

								behavior holds:


								    package Foo;

								    our $bar;		# declares $Foo::bar for rest of lexical scope

								    $bar = 20;


								    package Bar;

								    print $bar;		# prints 20


								Multiple C<our> declarations in the same lexical scope are allowed

								if they are in different packages.  If they happened to be in the same

								package, Perl will emit warnings if you have asked for them.


								    use warnings;

								    package Foo;

								    our $bar;		# declares $Foo::bar for rest of lexical scope

								    $bar = 20;


								    package Bar;

								    our $bar = 30;	# declares $Bar::bar for rest of lexical scope

								    print $bar;		# prints 30


								    our $bar;		# emits warning


								=item pack TEMPLATE,LIST


								Takes a LIST of values and converts it into a string using the rules

								given by the TEMPLATE.  The resulting string is the concatenation of

								the converted values.  Typically, each converted value looks

								like its machine-level representation.  For example, on 32-bit machines

								a converted integer may be represented by a sequence of 4 bytes.


								The TEMPLATE is a

								sequence of characters that give the order and type of values, as

								follows:


								    a	A string with arbitrary binary data, will be null padded.

								    A	An ASCII string, will be space padded.

								    Z	A null terminated (asciz) string, will be null padded.


								    b	A bit string (ascending bit order inside each byte, like vec()).

								    B	A bit string (descending bit order inside each byte).

								    h	A hex string (low nybble first).

								    H	A hex string (high nybble first).


								    c	A signed char value.

								    C	An unsigned char value.  Only does bytes.  See U for Unicode.


								    s	A signed short value.

								    S	An unsigned short value.

									  (This 'short' is _exactly_ 16 bits, which may differ from

									   what a local C compiler calls 'short'.  If you want

									   native-length shorts, use the '!' suffix.)


								    i	A signed integer value.

								    I	An unsigned integer value.

									  (This 'integer' is _at_least_ 32 bits wide.  Its exact

								           size depends on what a local C compiler calls 'int',

								           and may even be larger than the 'long' described in

								           the next item.)


								    l	A signed long value.

								    L	An unsigned long value.

									  (This 'long' is _exactly_ 32 bits, which may differ from

									   what a local C compiler calls 'long'.  If you want

									   native-length longs, use the '!' suffix.)


								    n	An unsigned short in "network" (big-endian) order.

								    N	An unsigned long in "network" (big-endian) order.

								    v	An unsigned short in "VAX" (little-endian) order.

								    V	An unsigned long in "VAX" (little-endian) order.

									  (These 'shorts' and 'longs' are _exactly_ 16 bits and

									   _exactly_ 32 bits, respectively.)


								    q	A signed quad (64-bit) value.

								    Q	An unsigned quad value.

									  (Quads are available only if your system supports 64-bit

									   integer values _and_ if Perl has been compiled to support those.

								           Causes a fatal error otherwise.)


								    f	A single-precision float in the native format.

								    d	A double-precision float in the native format.


								    p	A pointer to a null-terminated string.

								    P	A pointer to a structure (fixed-length string).


								    u	A uuencoded string.

								    U	A Unicode character number.  Encodes to UTF-8 internally.

									Works even if C<use utf8> is not in effect.


								    w	A BER compressed integer.  Its bytes represent an unsigned

									integer in base 128, most significant digit first, with as

								        few digits as possible.  Bit eight (the high bit) is set

								        on each byte except the last.


								    x	A null byte.

								    X	Back up a byte.

								    @	Null fill to absolute position.


								The following rules apply:


								=over 8


								=item *


								Each letter may optionally be followed by a number giving a repeat

								count.  With all types except C<a>, C<A>, C<Z>, C<b>, C<B>, C<h>,

								C<H>, and C<P> the pack function will gobble up that many values from

								the LIST.  A C<*> for the repeat count means to use however many items are

								left, except for C<@>, C<x>, C<X>, where it is equivalent

								to C<0>, and C<u>, where it is equivalent to 1 (or 45, what is the

								same).


								When used with C<Z>, C<*> results in the addition of a trailing null

								byte (so the packed result will be one longer than the byte C<length>

								of the item).


								The repeat count for C<u> is interpreted as the maximal number of bytes

								to encode per line of output, with 0 and 1 replaced by 45.


								=item *


								The C<a>, C<A>, and C<Z> types gobble just one value, but pack it as a

								string of length count, padding with nulls or spaces as necessary.  When

								unpacking, C<A> strips trailing spaces and nulls, C<Z> strips everything

								after the first null, and C<a> returns data verbatim.  When packing,

								C<a>, and C<Z> are equivalent.


								If the value-to-pack is too long, it is truncated.  If too long and an

								explicit count is provided, C<Z> packs only C<$count-1> bytes, followed

								by a null byte.  Thus C<Z> always packs a trailing null byte under

								all circumstances.


								=item *


								Likewise, the C<b> and C<B> fields pack a string that many bits long.

								Each byte of the input field of pack() generates 1 bit of the result.

								Each result bit is based on the least-significant bit of the corresponding

								input byte, i.e., on C<ord($byte)%2>.  In particular, bytes C<"0"> and

								C<"1"> generate bits 0 and 1, as do bytes C<"\0"> and C<"\1">.


								Starting from the beginning of the input string of pack(), each 8-tuple

								of bytes is converted to 1 byte of output.  With format C<b>

								the first byte of the 8-tuple determines the least-significant bit of a

								byte, and with format C<B> it determines the most-significant bit of

								a byte.


								If the length of the input string is not exactly divisible by 8, the

								remainder is packed as if the input string were padded by null bytes

								at the end.  Similarly, during unpack()ing the "extra" bits are ignored.


								If the input string of pack() is longer than needed, extra bytes are ignored.

								A C<*> for the repeat count of pack() means to use all the bytes of

								the input field.  On unpack()ing the bits are converted to a string

								of C<"0">s and C<"1">s.


								=item *


								The C<h> and C<H> fields pack a string that many nybbles (4-bit groups,

								representable as hexadecimal digits, 0-9a-f) long.


								Each byte of the input field of pack() generates 4 bits of the result.

								For non-alphabetical bytes the result is based on the 4 least-significant

								bits of the input byte, i.e., on C<ord($byte)%16>.  In particular,

								bytes C<"0"> and C<"1"> generate nybbles 0 and 1, as do bytes

								C<"\0"> and C<"\1">.  For bytes C<"a".."f"> and C<"A".."F"> the result

								is compatible with the usual hexadecimal digits, so that C<"a"> and

								C<"A"> both generate the nybble C<0xa==10>.  The result for bytes

								C<"g".."z"> and C<"G".."Z"> is not well-defined.


								Starting from the beginning of the input string of pack(), each pair

								of bytes is converted to 1 byte of output.  With format C<h> the

								first byte of the pair determines the least-significant nybble of the

								output byte, and with format C<H> it determines the most-significant

								nybble.


								If the length of the input string is not even, it behaves as if padded

								by a null byte at the end.  Similarly, during unpack()ing the "extra"

								nybbles are ignored.


								If the input string of pack() is longer than needed, extra bytes are ignored.

								A C<*> for the repeat count of pack() means to use all the bytes of

								the input field.  On unpack()ing the bits are converted to a string

								of hexadecimal digits.


								=item *


								The C<p> type packs a pointer to a null-terminated string.  You are

								responsible for ensuring the string is not a temporary value (which can

								potentially get deallocated before you get around to using the packed result).

								The C<P> type packs a pointer to a structure of the size indicated by the

								length.  A NULL pointer is created if the corresponding value for C<p> or

								C<P> is C<undef>, similarly for unpack().


								=item *


								The C</> template character allows packing and unpacking of strings where

								the packed structure contains a byte count followed by the string itself.

								You write I<length-item>C</>I<string-item>.


								The I<length-item> can be any C<pack> template letter,

								and describes how the length value is packed.

								The ones likely to be of most use are integer-packing ones like

								C<n> (for Java strings), C<w> (for ASN.1 or SNMP)

								and C<N> (for Sun XDR).


								The I<string-item> must, at present, be C<"A*">, C<"a*"> or C<"Z*">.

								For C<unpack> the length of the string is obtained from the I<length-item>,

								but if you put in the '*' it will be ignored.


								    unpack 'C/a', "\04Gurusamy";        gives 'Guru'

								    unpack 'a3/A* A*', '007 Bond  J ';  gives (' Bond','J')

								    pack 'n/a* w/a*','hello,','world';  gives "\000\006hello,\005world"


								The I<length-item> is not returned explicitly from C<unpack>.


								Adding a count to the I<length-item> letter is unlikely to do anything

								useful, unless that letter is C<A>, C<a> or C<Z>.  Packing with a

								I<length-item> of C<a> or C<Z> may introduce C<"\000"> characters,

								which Perl does not regard as legal in numeric strings.


								=item *


								The integer types C<s>, C<S>, C<l>, and C<L> may be

								immediately followed by a C<!> suffix to signify native shorts or

								longs--as you can see from above for example a bare C<l> does mean

								exactly 32 bits, the native C<long> (as seen by the local C compiler)

								may be larger.  This is an issue mainly in 64-bit platforms.  You can

								see whether using C<!> makes any difference by


									print length(pack("s")), " ", length(pack("s!")), "\n";

									print length(pack("l")), " ", length(pack("l!")), "\n";


								C<i!> and C<I!> also work but only because of completeness;

								they are identical to C<i> and C<I>.


								The actual sizes (in bytes) of native shorts, ints, longs, and long

								longs on the platform where Perl was built are also available via

								L<Config>:


								       use Config;

								       print $Config{shortsize},    "\n";

								       print $Config{intsize},      "\n";

								       print $Config{longsize},     "\n";

								       print $Config{longlongsize}, "\n";


								(The C<$Config{longlongsize}> will be undefine if your system does

								not support long longs.)


								=item *


								The integer formats C<s>, C<S>, C<i>, C<I>, C<l>, and C<L>

								are inherently non-portable between processors and operating systems

								because they obey the native byteorder and endianness.  For example a

								4-byte integer 0x12345678 (305419896 decimal) be ordered natively

								(arranged in and handled by the CPU registers) into bytes as


								 	0x12 0x34 0x56 0x78	# big-endian

								 	0x78 0x56 0x34 0x12	# little-endian


								Basically, the Intel and VAX CPUs are little-endian, while everybody

								else, for example Motorola m68k/88k, PPC, Sparc, HP PA, Power, and

								Cray are big-endian.  Alpha and MIPS can be either: Digital/Compaq

								used/uses them in little-endian mode; SGI/Cray uses them in big-endian mode.


								The names `big-endian' and `little-endian' are comic references to

								the classic "Gulliver's Travels" (via the paper "On Holy Wars and a

								Plea for Peace" by Danny Cohen, USC/ISI IEN 137, April 1, 1980) and

								the egg-eating habits of the Lilliputians.


								Some systems may have even weirder byte orders such as


								 	0x56 0x78 0x12 0x34

								 	0x34 0x12 0x78 0x56


								You can see your system's preference with


								 	print join(" ", map { sprintf "%#02x", $_ }

								                            unpack("C*",pack("L",0x12345678))), "\n";


								The byteorder on the platform where Perl was built is also available

								via L<Config>:


									use Config;

									print $Config{byteorder}, "\n";


								Byteorders C<'1234'> and C<'12345678'> are little-endian, C<'4321'>

								and C<'87654321'> are big-endian.


								If you want portable packed integers use the formats C<n>, C<N>,

								C<v>, and C<V>, their byte endianness and size is known.

								See also L<perlport>.


								=item *


								Real numbers (floats and doubles) are in the native machine format only;

								due to the multiplicity of floating formats around, and the lack of a

								standard "network" representation, no facility for interchange has been

								made.  This means that packed floating point data written on one machine

								may not be readable on another - even if both use IEEE floating point

								arithmetic (as the endian-ness of the memory representation is not part

								of the IEEE spec).  See also L<perlport>.


								Note that Perl uses doubles internally for all numeric calculation, and

								converting from double into float and thence back to double again will

								lose precision (i.e., C<unpack("f", pack("f", $foo)>) will not in general

								equal $foo).


								=item *


								If the pattern begins with a C<U>, the resulting string will be treated

								as Unicode-encoded. You can force UTF8 encoding on in a string with an

								initial C<U0>, and the bytes that follow will be interpreted as Unicode

								characters. If you don't want this to happen, you can begin your pattern

								with C<C0> (or anything else) to force Perl not to UTF8 encode your

								string, and then follow this with a C<U*> somewhere in your pattern.


								=item *


								You must yourself do any alignment or padding by inserting for example

								enough C<'x'>es while packing.  There is no way to pack() and unpack()

								could know where the bytes are going to or coming from.  Therefore

								C<pack> (and C<unpack>) handle their output and input as flat

								sequences of bytes.


								=item *


								A comment in a TEMPLATE starts with C<#> and goes to the end of line.


								=item *


								If TEMPLATE requires more arguments to pack() than actually given, pack()

								assumes additional C<""> arguments.  If TEMPLATE requires less arguments

								to pack() than actually given, extra arguments are ignored.


								=back


								Examples:


								    $foo = pack("CCCC",65,66,67,68);

								    # foo eq "ABCD"

								    $foo = pack("C4",65,66,67,68);

								    # same thing

								    $foo = pack("U4",0x24b6,0x24b7,0x24b8,0x24b9);

								    # same thing with Unicode circled letters


								    $foo = pack("ccxxcc",65,66,67,68);

								    # foo eq "AB\0\0CD"


								    # note: the above examples featuring "C" and "c" are true

								    # only on ASCII and ASCII-derived systems such as ISO Latin 1

								    # and UTF-8.  In EBCDIC the first example would be

								    # $foo = pack("CCCC",193,194,195,196);


								    $foo = pack("s2",1,2);

								    # "\1\0\2\0" on little-endian

								    # "\0\1\0\2" on big-endian


								    $foo = pack("a4","abcd","x","y","z");

								    # "abcd"


								    $foo = pack("aaaa","abcd","x","y","z");

								    # "axyz"


								    $foo = pack("a14","abcdefg");

								    # "abcdefg\0\0\0\0\0\0\0"


								    $foo = pack("i9pl", gmtime);

								    # a real struct tm (on my system anyway)


								    $utmp_template = "Z8 Z8 Z16 L";

								    $utmp = pack($utmp_template, @utmp1);

								    # a struct utmp (BSDish)


								    @utmp2 = unpack($utmp_template, $utmp);

								    # "@utmp1" eq "@utmp2"


								    sub bintodec {

									unpack("N", pack("B32", substr("0" x 32 . shift, -32)));

								    }


								    $foo = pack('sx2l', 12, 34);

								    # short 12, two zero bytes padding, long 34

								    $bar = pack('s@4l', 12, 34);

								    # short 12, zero fill to position 4, long 34

								    # $foo eq $bar


								The same template may generally also be used in unpack().


								=item package NAMESPACE


								=item package


								Declares the compilation unit as being in the given namespace.  The scope

								of the package declaration is from the declaration itself through the end

								of the enclosing block, file, or eval (the same as the C<my> operator).

								All further unqualified dynamic identifiers will be in this namespace.

								A package statement affects only dynamic variables--including those

								you've used C<local> on--but I<not> lexical variables, which are created

								with C<my>.  Typically it would be the first declaration in a file to

								be included by the C<require> or C<use> operator.  You can switch into a

								package in more than one place; it merely influences which symbol table

								is used by the compiler for the rest of that block.  You can refer to

								variables and filehandles in other packages by prefixing the identifier

								with the package name and a double colon:  C<$Package::Variable>.

								If the package name is null, the C<main> package as assumed.  That is,

								C<$::sail> is equivalent to C<$main::sail> (as well as to C<$main'sail>,

								still seen in older code).


								If NAMESPACE is omitted, then there is no current package, and all

								identifiers must be fully qualified or lexicals.  This is stricter

								than C<use strict>, since it also extends to function names.


								See L<perlmod/"Packages"> for more information about packages, modules,

								and classes.  See L<perlsub> for other scoping issues.


								=item pipe READHANDLE,WRITEHANDLE


								Opens a pair of connected pipes like the corresponding system call.

								Note that if you set up a loop of piped processes, deadlock can occur

								unless you are very careful.  In addition, note that Perl's pipes use

								stdio buffering, so you may need to set C<$|> to flush your WRITEHANDLE

								after each command, depending on the application.


								See L<IPC::Open2>, L<IPC::Open3>, and L<perlipc/"Bidirectional Communication">

								for examples of such things.


								On systems that support a close-on-exec flag on files, the flag will be set

								for the newly opened file descriptors as determined by the value of $^F.

								See L<perlvar/$^F>.


								=item pop ARRAY


								=item pop


								Pops and returns the last value of the array, shortening the array by

								one element.  Has an effect similar to


								    $ARRAY[$#ARRAY--]


								If there are no elements in the array, returns the undefined value

								(although this may happen at other times as well).  If ARRAY is

								omitted, pops the C<@ARGV> array in the main program, and the C<@_>

								array in subroutines, just like C<shift>.


								=item pos SCALAR


								=item pos


								Returns the offset of where the last C<m//g> search left off for the variable

								in question (C<$_> is used when the variable is not specified).  May be

								modified to change that offset.  Such modification will also influence

								the C<\G> zero-width assertion in regular expressions.  See L<perlre> and

								L<perlop>.


								=item print FILEHANDLE LIST


								=item print LIST


								=item print


								Prints a string or a list of strings.  Returns true if successful.

								FILEHANDLE may be a scalar variable name, in which case the variable

								contains the name of or a reference to the filehandle, thus introducing

								one level of indirection.  (NOTE: If FILEHANDLE is a variable and

								the next token is a term, it may be misinterpreted as an operator

								unless you interpose a C<+> or put parentheses around the arguments.)

								If FILEHANDLE is omitted, prints by default to standard output (or

								to the last selected output channel--see L</select>).  If LIST is

								also omitted, prints C<$_> to the currently selected output channel.

								To set the default output channel to something other than STDOUT

								use the select operation.  The current value of C<$,> (if any) is

								printed between each LIST item.  The current value of C<$\> (if

								any) is printed after the entire LIST has been printed.  Because

								print takes a LIST, anything in the LIST is evaluated in list

								context, and any subroutine that you call will have one or more of

								its expressions evaluated in list context.  Also be careful not to

								follow the print keyword with a left parenthesis unless you want

								the corresponding right parenthesis to terminate the arguments to

								the print--interpose a C<+> or put parentheses around all the

								arguments.


								Note that if you're storing FILEHANDLES in an array or other expression,

								you will have to use a block returning its value instead:


								    print { $files[$i] } "stuff\n";

								    print { $OK ? STDOUT : STDERR } "stuff\n";


								=item printf FILEHANDLE FORMAT, LIST


								=item printf FORMAT, LIST


								Equivalent to C<print FILEHANDLE sprintf(FORMAT, LIST)>, except that C<$\>

								(the output record separator) is not appended.  The first argument

								of the list will be interpreted as the C<printf> format.  If C<use locale> is

								in effect, the character used for the decimal point in formatted real numbers

								is affected by the LC_NUMERIC locale.  See L<perllocale>.


								Don't fall into the trap of using a C<printf> when a simple

								C<print> would do.  The C<print> is more efficient and less

								error prone.


								=item prototype FUNCTION


								Returns the prototype of a function as a string (or C<undef> if the

								function has no prototype).  FUNCTION is a reference to, or the name of,

								the function whose prototype you want to retrieve.


								If FUNCTION is a string starting with C<CORE::>, the rest is taken as a

								name for Perl builtin.  If the builtin is not I<overridable> (such as

								C<qw//>) or its arguments cannot be expressed by a prototype (such as

								C<system>) returns C<undef> because the builtin does not really behave

								like a Perl function.  Otherwise, the string describing the equivalent

								prototype is returned.


								=item push ARRAY,LIST


								Treats ARRAY as a stack, and pushes the values of LIST

								onto the end of ARRAY.  The length of ARRAY increases by the length of

								LIST.  Has the same effect as


								    for $value (LIST) {

									$ARRAY[++$#ARRAY] = $value;

								    }


								but is more efficient.  Returns the new number of elements in the array.


								=item q/STRING/


								=item qq/STRING/


								=item qr/STRING/


								=item qx/STRING/


								=item qw/STRING/


								Generalized quotes.  See L<perlop/"Regexp Quote-Like Operators">.


								=item quotemeta EXPR


								=item quotemeta


								Returns the value of EXPR with all non-"word"

								characters backslashed.  (That is, all characters not matching

								C</[A-Za-z_0-9]/> will be preceded by a backslash in the

								returned string, regardless of any locale settings.)

								This is the internal function implementing

								the C<\Q> escape in double-quoted strings.


								If EXPR is omitted, uses C<$_>.


								=item rand EXPR


								=item rand


								Returns a random fractional number greater than or equal to C<0> and less

								than the value of EXPR.  (EXPR should be positive.)  If EXPR is

								omitted, the value C<1> is used.  Automatically calls C<srand> unless

								C<srand> has already been called.  See also C<srand>.


								(Note: If your rand function consistently returns numbers that are too

								large or too small, then your version of Perl was probably compiled

								with the wrong number of RANDBITS.)


								=item read FILEHANDLE,SCALAR,LENGTH,OFFSET


								=item read FILEHANDLE,SCALAR,LENGTH


								Attempts to read LENGTH bytes of data into variable SCALAR from the

								specified FILEHANDLE.  Returns the number of bytes actually read, C<0>

								at end of file, or undef if there was an error.  SCALAR will be grown

								or shrunk to the length actually read.  If SCALAR needs growing, the

								new bytes will be zero bytes.  An OFFSET may be specified to place

								the read data into some other place in SCALAR than the beginning.

								The call is actually implemented in terms of stdio's fread(3) call.

								To get a true read(2) system call, see C<sysread>.


								=item readdir DIRHANDLE


								Returns the next directory entry for a directory opened by C<opendir>.

								If used in list context, returns all the rest of the entries in the

								directory.  If there are no more entries, returns an undefined value in

								scalar context or a null list in list context.


								If you're planning to filetest the return values out of a C<readdir>, you'd

								better prepend the directory in question.  Otherwise, because we didn't

								C<chdir> there, it would have been testing the wrong file.


								    opendir(DIR, $some_dir) || die "can't opendir $some_dir: $!";

								    @dots = grep { /^\./ && -f "$some_dir/$_" } readdir(DIR);

								    closedir DIR;


								=item readline EXPR


								Reads from the filehandle whose typeglob is contained in EXPR.  In scalar

								context, each call reads and returns the next line, until end-of-file is

								reached, whereupon the subsequent call returns undef.  In list context,

								reads until end-of-file is reached and returns a list of lines.  Note that

								the notion of "line" used here is however you may have defined it

								with C<$/> or C<$INPUT_RECORD_SEPARATOR>).  See L<perlvar/"$/">.


								When C<$/> is set to C<undef>, when readline() is in scalar

								context (i.e. file slurp mode), and when an empty file is read, it

								returns C<''> the first time, followed by C<undef> subsequently.


								This is the internal function implementing the C<< <EXPR> >>

								operator, but you can use it directly.  The C<< <EXPR> >>

								operator is discussed in more detail in L<perlop/"I/O Operators">.


								    $line = <STDIN>;

								    $line = readline(*STDIN);		# same thing


								=item readlink EXPR


								=item readlink


								Returns the value of a symbolic link, if symbolic links are

								implemented.  If not, gives a fatal error.  If there is some system

								error, returns the undefined value and sets C<$!> (errno).  If EXPR is

								omitted, uses C<$_>.


								=item readpipe EXPR


								EXPR is executed as a system command.

								The collected standard output of the command is returned.

								In scalar context, it comes back as a single (potentially

								multi-line) string.  In list context, returns a list of lines

								(however you've defined lines with C<$/> or C<$INPUT_RECORD_SEPARATOR>).

								This is the internal function implementing the C<qx/EXPR/>

								operator, but you can use it directly.  The C<qx/EXPR/>

								operator is discussed in more detail in L<perlop/"I/O Operators">.


								=item recv SOCKET,SCALAR,LENGTH,FLAGS


								Receives a message on a socket.  Attempts to receive LENGTH bytes of

								data into variable SCALAR from the specified SOCKET filehandle.  SCALAR

								will be grown or shrunk to the length actually read.  Takes the same

								flags as the system call of the same name.  Returns the address of the

								sender if SOCKET's protocol supports this; returns an empty string

								otherwise.  If there's an error, returns the undefined value.  This call

								is actually implemented in terms of recvfrom(2) system call.  See

								L<perlipc/"UDP: Message Passing"> for examples.


								=item redo LABEL


								=item redo


								The C<redo> command restarts the loop block without evaluating the

								conditional again.  The C<continue> block, if any, is not executed.  If

								the LABEL is omitted, the command refers to the innermost enclosing

								loop.  This command is normally used by programs that want to lie to

								themselves about what was just input:


								    # a simpleminded Pascal comment stripper

								    # (warning: assumes no { or } in strings)

								    LINE: while (<STDIN>) {

									while (s|({.*}.*){.*}|$1 |) {}

									s|{.*}| |;

									if (s|{.*| |) {

									    $front = $_;

									    while (<STDIN>) {

										if (/}/) {	# end of comment?

										    s|^|$front\{|;

										    redo LINE;

										}

									    }

									}

									print;

								    }


								C<redo> cannot be used to retry a block which returns a value such as

								C<eval {}>, C<sub {}> or C<do {}>, and should not be used to exit

								a grep() or map() operation.


								Note that a block by itself is semantically identical to a loop

								that executes once.  Thus C<redo> inside such a block will effectively

								turn it into a looping construct.


								See also L</continue> for an illustration of how C<last>, C<next>, and

								C<redo> work.


								=item ref EXPR


								=item ref


								Returns a true value if EXPR is a reference, false otherwise.  If EXPR

								is not specified, C<$_> will be used.  The value returned depends on the

								type of thing the reference is a reference to.

								Builtin types include:


								    SCALAR

								    ARRAY

								    HASH

								    CODE

								    REF

								    GLOB

								    LVALUE


								If the referenced object has been blessed into a package, then that package

								name is returned instead.  You can think of C<ref> as a C<typeof> operator.


								    if (ref($r) eq "HASH") {

									print "r is a reference to a hash.\n";

								    }

								    unless (ref($r)) {

									print "r is not a reference at all.\n";

								    }

								    if (UNIVERSAL::isa($r, "HASH")) {  # for subclassing

									print "r is a reference to something that isa hash.\n";

								    }


								See also L<perlref>.


								=item rename OLDNAME,NEWNAME


								Changes the name of a file; an existing file NEWNAME will be

								clobbered.  Returns true for success, false otherwise.


								Behavior of this function varies wildly depending on your system

								implementation.  For example, it will usually not work across file system

								boundaries, even though the system I<mv> command sometimes compensates

								for this.  Other restrictions include whether it works on directories,

								open files, or pre-existing files.  Check L<perlport> and either the

								rename(2) manpage or equivalent system documentation for details.


								=item require VERSION


								=item require EXPR


								=item require


								Demands some semantics specified by EXPR, or by C<$_> if EXPR is not

								supplied.


								If a VERSION is specified as a literal of the form v5.6.1,

								demands that the current version of Perl (C<$^V> or $PERL_VERSION) be

								at least as recent as that version, at run time.  (For compatibility

								with older versions of Perl, a numeric argument will also be interpreted

								as VERSION.)  Compare with L</use>, which can do a similar check at

								compile time.


								    require v5.6.1;	# run time version check

								    require 5.6.1;	# ditto

								    require 5.005_03;	# float version allowed for compatibility


								Otherwise, demands that a library file be included if it hasn't already

								been included.  The file is included via the do-FILE mechanism, which is

								essentially just a variety of C<eval>.  Has semantics similar to the following

								subroutine:


								    sub require {

									my($filename) = @_;

									return 1 if $INC{$filename};

									my($realfilename,$result);

									ITER: {

									    foreach $prefix (@INC) {

										$realfilename = "$prefix/$filename";

										if (-f $realfilename) {

										    $INC{$filename} = $realfilename;

										    $result = do $realfilename;

										    last ITER;

										}

									    }

									    die "Can't find $filename in \@INC";

									}

									delete $INC{$filename} if $@ || !$result;

									die $@ if $@;

									die "$filename did not return true value" unless $result;

									return $result;

								    }


								Note that the file will not be included twice under the same specified

								name.  The file must return true as the last statement to indicate

								successful execution of any initialization code, so it's customary to

								end such a file with C<1;> unless you're sure it'll return true

								otherwise.  But it's better just to put the C<1;>, in case you add more

								statements.


								If EXPR is a bareword, the require assumes a "F<.pm>" extension and

								replaces "F<::>" with "F</>" in the filename for you,

								to make it easy to load standard modules.  This form of loading of

								modules does not risk altering your namespace.


								In other words, if you try this:


								        require Foo::Bar;    # a splendid bareword


								The require function will actually look for the "F<Foo/Bar.pm>" file in the

								directories specified in the C<@INC> array.


								But if you try this:


								        $class = 'Foo::Bar';

								        require $class;	     # $class is not a bareword

								    #or

								        require "Foo::Bar";  # not a bareword because of the ""


								The require function will look for the "F<Foo::Bar>" file in the @INC array and

								will complain about not finding "F<Foo::Bar>" there.  In this case you can do:


								        eval "require $class";


								For a yet-more-powerful import facility, see L</use> and L<perlmod>.


								=item reset EXPR


								=item reset


								Generally used in a C<continue> block at the end of a loop to clear

								variables and reset C<??> searches so that they work again.  The

								expression is interpreted as a list of single characters (hyphens

								allowed for ranges).  All variables and arrays beginning with one of

								those letters are reset to their pristine state.  If the expression is

								omitted, one-match searches (C<?pattern?>) are reset to match again.  Resets

								only variables or searches in the current package.  Always returns

								1.  Examples:


								    reset 'X';		# reset all X variables

								    reset 'a-z';	# reset lower case variables

								    reset;		# just reset ?one-time? searches


								Resetting C<"A-Z"> is not recommended because you'll wipe out your

								C<@ARGV> and C<@INC> arrays and your C<%ENV> hash.  Resets only package

								variables--lexical variables are unaffected, but they clean themselves

								up on scope exit anyway, so you'll probably want to use them instead.

								See L</my>.


								=item return EXPR


								=item return


								Returns from a subroutine, C<eval>, or C<do FILE> with the value

								given in EXPR.  Evaluation of EXPR may be in list, scalar, or void

								context, depending on how the return value will be used, and the context

								may vary from one execution to the next (see C<wantarray>).  If no EXPR

								is given, returns an empty list in list context, the undefined value in

								scalar context, and (of course) nothing at all in a void context.


								(Note that in the absence of a explicit C<return>, a subroutine, eval,

								or do FILE will automatically return the value of the last expression

								evaluated.)


								=item reverse LIST


								In list context, returns a list value consisting of the elements

								of LIST in the opposite order.  In scalar context, concatenates the

								elements of LIST and returns a string value with all characters

								in the opposite order.


								    print reverse <>;		# line tac, last line first


								    undef $/;			# for efficiency of <>

								    print scalar reverse <>;	# character tac, last line tsrif


								This operator is also handy for inverting a hash, although there are some

								caveats.  If a value is duplicated in the original hash, only one of those

								can be represented as a key in the inverted hash.  Also, this has to

								unwind one hash and build a whole new one, which may take some time

								on a large hash, such as from a DBM file.


								    %by_name = reverse %by_address;	# Invert the hash


								=item rewinddir DIRHANDLE


								Sets the current position to the beginning of the directory for the

								C<readdir> routine on DIRHANDLE.


								=item rindex STR,SUBSTR,POSITION


								=item rindex STR,SUBSTR


								Works just like index() except that it returns the position of the LAST

								occurrence of SUBSTR in STR.  If POSITION is specified, returns the

								last occurrence at or before that position.


								=item rmdir FILENAME


								=item rmdir


								Deletes the directory specified by FILENAME if that directory is empty.  If it

								succeeds it returns true, otherwise it returns false and sets C<$!> (errno).  If

								FILENAME is omitted, uses C<$_>.


								=item s///


								The substitution operator.  See L<perlop>.


								=item scalar EXPR


								Forces EXPR to be interpreted in scalar context and returns the value

								of EXPR.


								    @counts = ( scalar @a, scalar @b, scalar @c );


								There is no equivalent operator to force an expression to

								be interpolated in list context because in practice, this is never

								needed.  If you really wanted to do so, however, you could use

								the construction C<@{[ (some expression) ]}>, but usually a simple

								C<(some expression)> suffices.


								Because C<scalar> is unary operator, if you accidentally use for EXPR a

								parenthesized list, this behaves as a scalar comma expression, evaluating

								all but the last element in void context and returning the final element

								evaluated in scalar context.  This is seldom what you want.


								The following single statement:


									print uc(scalar(&foo,$bar)),$baz;


								is the moral equivalent of these two:


									&foo;

									print(uc($bar),$baz);


								See L<perlop> for more details on unary operators and the comma operator.


								=item seek FILEHANDLE,POSITION,WHENCE


								Sets FILEHANDLE's position, just like the C<fseek> call of C<stdio>.

								FILEHANDLE may be an expression whose value gives the name of the

								filehandle.  The values for WHENCE are C<0> to set the new position to

								POSITION, C<1> to set it to the current position plus POSITION, and

								C<2> to set it to EOF plus POSITION (typically negative).  For WHENCE

								you may use the constants C<SEEK_SET>, C<SEEK_CUR>, and C<SEEK_END>

								(start of the file, current position, end of the file) from the Fcntl

								module.  Returns C<1> upon success, C<0> otherwise.


								If you want to position file for C<sysread> or C<syswrite>, don't use

								C<seek>--buffering makes its effect on the file's system position

								unpredictable and non-portable.  Use C<sysseek> instead.


								Due to the rules and rigors of ANSI C, on some systems you have to do a

								seek whenever you switch between reading and writing.  Amongst other

								things, this may have the effect of calling stdio's clearerr(3).

								A WHENCE of C<1> (C<SEEK_CUR>) is useful for not moving the file position:


								    seek(TEST,0,1);


								This is also useful for applications emulating C<tail -f>.  Once you hit

								EOF on your read, and then sleep for a while, you might have to stick in a

								seek() to reset things.  The C<seek> doesn't change the current position,

								but it I<does> clear the end-of-file condition on the handle, so that the

								next C<< <FILE> >> makes Perl try again to read something.  We hope.


								If that doesn't work (some stdios are particularly cantankerous), then

								you may need something more like this:


								    for (;;) {

									for ($curpos = tell(FILE); $_ = <FILE>;

								             $curpos = tell(FILE)) {

									    # search for some stuff and put it into files

									}

									sleep($for_a_while);

									seek(FILE, $curpos, 0);

								    }


								=item seekdir DIRHANDLE,POS


								Sets the current position for the C<readdir> routine on DIRHANDLE.  POS

								must be a value returned by C<telldir>.  Has the same caveats about

								possible directory compaction as the corresponding system library

								routine.


								=item select FILEHANDLE


								=item select


								Returns the currently selected filehandle.  Sets the current default

								filehandle for output, if FILEHANDLE is supplied.  This has two

								effects: first, a C<write> or a C<print> without a filehandle will

								default to this FILEHANDLE.  Second, references to variables related to

								output will refer to this output channel.  For example, if you have to

								set the top of form format for more than one output channel, you might

								do the following:


								    select(REPORT1);

								    $^ = 'report1_top';

								    select(REPORT2);

								    $^ = 'report2_top';


								FILEHANDLE may be an expression whose value gives the name of the

								actual filehandle.  Thus:


								    $oldfh = select(STDERR); $| = 1; select($oldfh);


								Some programmers may prefer to think of filehandles as objects with

								methods, preferring to write the last example as:


								    use IO::Handle;

								    STDERR->autoflush(1);


								=item select RBITS,WBITS,EBITS,TIMEOUT


								This calls the select(2) system call with the bit masks specified, which

								can be constructed using C<fileno> and C<vec>, along these lines:


								    $rin = $win = $ein = '';

								    vec($rin,fileno(STDIN),1) = 1;

								    vec($win,fileno(STDOUT),1) = 1;

								    $ein = $rin | $win;


								If you want to select on many filehandles you might wish to write a

								subroutine:


								    sub fhbits {

									my(@fhlist) = split(' ',$_[0]);

									my($bits);

									for (@fhlist) {

									    vec($bits,fileno($_),1) = 1;

									}

									$bits;

								    }

								    $rin = fhbits('STDIN TTY SOCK');


								The usual idiom is:


								    ($nfound,$timeleft) =

								      select($rout=$rin, $wout=$win, $eout=$ein, $timeout);


								or to block until something becomes ready just do this


								    $nfound = select($rout=$rin, $wout=$win, $eout=$ein, undef);


								Most systems do not bother to return anything useful in $timeleft, so

								calling select() in scalar context just returns $nfound.


								Any of the bit masks can also be undef.  The timeout, if specified, is

								in seconds, which may be fractional.  Note: not all implementations are

								capable of returning the$timeleft.  If not, they always return

								$timeleft equal to the supplied $timeout.


								You can effect a sleep of 250 milliseconds this way:


								    select(undef, undef, undef, 0.25);


								B<WARNING>: One should not attempt to mix buffered I/O (like C<read>

								or <FH>) with C<select>, except as permitted by POSIX, and even

								then only on POSIX systems.  You have to use C<sysread> instead.


								=item semctl ID,SEMNUM,CMD,ARG


								Calls the System V IPC function C<semctl>.  You'll probably have to say


								    use IPC::SysV;


								first to get the correct constant definitions.  If CMD is IPC_STAT or

								GETALL, then ARG must be a variable which will hold the returned

								semid_ds structure or semaphore value array.  Returns like C<ioctl>:

								the undefined value for error, "C<0 but true>" for zero, or the actual

								return value otherwise.  The ARG must consist of a vector of native

								short integers, which may be created with C<pack("s!",(0)x$nsem)>.

								See also L<perlipc/"SysV IPC">, C<IPC::SysV>, C<IPC::Semaphore>

								documentation.


								=item semget KEY,NSEMS,FLAGS


								Calls the System V IPC function semget.  Returns the semaphore id, or

								the undefined value if there is an error.  See also

								L<perlipc/"SysV IPC">, C<IPC::SysV>, C<IPC::SysV::Semaphore>

								documentation.


								=item semop KEY,OPSTRING


								Calls the System V IPC function semop to perform semaphore operations

								such as signaling and waiting.  OPSTRING must be a packed array of

								semop structures.  Each semop structure can be generated with

								C<pack("sss", $semnum, $semop, $semflag)>.  The number of semaphore

								operations is implied by the length of OPSTRING.  Returns true if

								successful, or false if there is an error.  As an example, the

								following code waits on semaphore $semnum of semaphore id $semid:


								    $semop = pack("sss", $semnum, -1, 0);

								    die "Semaphore trouble: $!\n" unless semop($semid, $semop);


								To signal the semaphore, replace C<-1> with C<1>.  See also

								L<perlipc/"SysV IPC">, C<IPC::SysV>, and C<IPC::SysV::Semaphore>

								documentation.


								=item send SOCKET,MSG,FLAGS,TO


								=item send SOCKET,MSG,FLAGS


								Sends a message on a socket.  Takes the same flags as the system call

								of the same name.  On unconnected sockets you must specify a

								destination to send TO, in which case it does a C C<sendto>.  Returns

								the number of characters sent, or the undefined value if there is an

								error.  The C system call sendmsg(2) is currently unimplemented.

								See L<perlipc/"UDP: Message Passing"> for examples.


								=item setpgrp PID,PGRP


								Sets the current process group for the specified PID, C<0> for the current

								process.  Will produce a fatal error if used on a machine that doesn't

								implement POSIX setpgid(2) or BSD setpgrp(2).  If the arguments are omitted,

								it defaults to C<0,0>.  Note that the BSD 4.2 version of C<setpgrp> does not

								accept any arguments, so only C<setpgrp(0,0)> is portable.  See also

								C<POSIX::setsid()>.


								=item setpriority WHICH,WHO,PRIORITY


								Sets the current priority for a process, a process group, or a user.

								(See setpriority(2).)  Will produce a fatal error if used on a machine

								that doesn't implement setpriority(2).


								=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL


								Sets the socket option requested.  Returns undefined if there is an

								error.  OPTVAL may be specified as C<undef> if you don't want to pass an

								argument.


								=item shift ARRAY


								=item shift


								Shifts the first value of the array off and returns it, shortening the

								array by 1 and moving everything down.  If there are no elements in the

								array, returns the undefined value.  If ARRAY is omitted, shifts the

								C<@_> array within the lexical scope of subroutines and formats, and the

								C<@ARGV> array at file scopes or within the lexical scopes established by

								the C<eval ''>, C<BEGIN {}>, C<INIT {}>, C<CHECK {}>, and C<END {}>

								constructs.


								See also C<unshift>, C<push>, and C<pop>.  C<shift> and C<unshift> do the

								same thing to the left end of an array that C<pop> and C<push> do to the

								right end.


								=item shmctl ID,CMD,ARG


								Calls the System V IPC function shmctl.  You'll probably have to say


								    use IPC::SysV;


								first to get the correct constant definitions.  If CMD is C<IPC_STAT>,

								then ARG must be a variable which will hold the returned C<shmid_ds>

								structure.  Returns like ioctl: the undefined value for error, "C<0> but

								true" for zero, or the actual return value otherwise.

								See also L<perlipc/"SysV IPC"> and C<IPC::SysV> documentation.


								=item shmget KEY,SIZE,FLAGS


								Calls the System V IPC function shmget.  Returns the shared memory

								segment id, or the undefined value if there is an error.

								See also L<perlipc/"SysV IPC"> and C<IPC::SysV> documentation.


								=item shmread ID,VAR,POS,SIZE


								=item shmwrite ID,STRING,POS,SIZE


								Reads or writes the System V shared memory segment ID starting at

								position POS for size SIZE by attaching to it, copying in/out, and

								detaching from it.  When reading, VAR must be a variable that will

								hold the data read.  When writing, if STRING is too long, only SIZE

								bytes are used; if STRING is too short, nulls are written to fill out

								SIZE bytes.  Return true if successful, or false if there is an error.

								shmread() taints the variable. See also L<perlipc/"SysV IPC">,

								C<IPC::SysV> documentation, and the C<IPC::Shareable> module from CPAN.


								=item shutdown SOCKET,HOW


								Shuts down a socket connection in the manner indicated by HOW, which

								has the same interpretation as in the system call of the same name.


								    shutdown(SOCKET, 0);    # I/we have stopped reading data

								    shutdown(SOCKET, 1);    # I/we have stopped writing data

								    shutdown(SOCKET, 2);    # I/we have stopped using this socket


								This is useful with sockets when you want to tell the other

								side you're done writing but not done reading, or vice versa.

								It's also a more insistent form of close because it also

								disables the file descriptor in any forked copies in other

								processes.


								=item sin EXPR


								=item sin


								Returns the sine of EXPR (expressed in radians).  If EXPR is omitted,

								returns sine of C<$_>.


								For the inverse sine operation, you may use the C<Math::Trig::asin>

								function, or use this relation:


								    sub asin { atan2($_[0], sqrt(1 - $_[0] * $_[0])) }


								=item sleep EXPR


								=item sleep


								Causes the script to sleep for EXPR seconds, or forever if no EXPR.

								May be interrupted if the process receives a signal such as C<SIGALRM>.

								Returns the number of seconds actually slept.  You probably cannot

								mix C<alarm> and C<sleep> calls, because C<sleep> is often implemented

								using C<alarm>.


								On some older systems, it may sleep up to a full second less than what

								you requested, depending on how it counts seconds.  Most modern systems

								always sleep the full amount.  They may appear to sleep longer than that,

								however, because your process might not be scheduled right away in a

								busy multitasking system.


								For delays of finer granularity than one second, you may use Perl's

								C<syscall> interface to access setitimer(2) if your system supports

								it, or else see L</select> above.  The Time::HiRes module from CPAN

								may also help.


								See also the POSIX module's C<pause> function.


								=item socket SOCKET,DOMAIN,TYPE,PROTOCOL


								Opens a socket of the specified kind and attaches it to filehandle

								SOCKET.  DOMAIN, TYPE, and PROTOCOL are specified the same as for

								the system call of the same name.  You should C<use Socket> first

								to get the proper definitions imported.  See the examples in

								L<perlipc/"Sockets: Client/Server Communication">.


								On systems that support a close-on-exec flag on files, the flag will

								be set for the newly opened file descriptor, as determined by the

								value of $^F.  See L<perlvar/$^F>.


								=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL


								Creates an unnamed pair of sockets in the specified domain, of the

								specified type.  DOMAIN, TYPE, and PROTOCOL are specified the same as

								for the system call of the same name.  If unimplemented, yields a fatal

								error.  Returns true if successful.


								On systems that support a close-on-exec flag on files, the flag will

								be set for the newly opened file descriptors, as determined by the value

								of $^F.  See L<perlvar/$^F>.


								Some systems defined C<pipe> in terms of C<socketpair>, in which a call

								to C<pipe(Rdr, Wtr)> is essentially:


								    use Socket;

								    socketpair(Rdr, Wtr, AF_UNIX, SOCK_STREAM, PF_UNSPEC);

								    shutdown(Rdr, 1);        # no more writing for reader

								    shutdown(Wtr, 0);        # no more reading for writer


								See L<perlipc> for an example of socketpair use.


								=item sort SUBNAME LIST


								=item sort BLOCK LIST


								=item sort LIST


								Sorts the LIST and returns the sorted list value.  If SUBNAME or BLOCK

								is omitted, C<sort>s in standard string comparison order.  If SUBNAME is

								specified, it gives the name of a subroutine that returns an integer

								less than, equal to, or greater than C<0>, depending on how the elements

								of the list are to be ordered.  (The C<< <=> >> and C<cmp>

								operators are extremely useful in such routines.)  SUBNAME may be a

								scalar variable name (unsubscripted), in which case the value provides

								the name of (or a reference to) the actual subroutine to use.  In place

								of a SUBNAME, you can provide a BLOCK as an anonymous, in-line sort

								subroutine.


								If the subroutine's prototype is C<($$)>, the elements to be compared

								are passed by reference in C<@_>, as for a normal subroutine.  This is

								slower than unprototyped subroutines, where the elements to be

								compared are passed into the subroutine

								as the package global variables $a and $b (see example below).  Note that

								in the latter case, it is usually counter-productive to declare $a and

								$b as lexicals.


								In either case, the subroutine may not be recursive.  The values to be

								compared are always passed by reference, so don't modify them.


								You also cannot exit out of the sort block or subroutine using any of the

								loop control operators described in L<perlsyn> or with C<goto>.


								When C<use locale> is in effect, C<sort LIST> sorts LIST according to the

								current collation locale.  See L<perllocale>.


								Examples:


								    # sort lexically

								    @articles = sort @files;


								    # same thing, but with explicit sort routine

								    @articles = sort {$a cmp $b} @files;


								    # now case-insensitively

								    @articles = sort {uc($a) cmp uc($b)} @files;


								    # same thing in reversed order

								    @articles = sort {$b cmp $a} @files;


								    # sort numerically ascending

								    @articles = sort {$a <=> $b} @files;


								    # sort numerically descending

								    @articles = sort {$b <=> $a} @files;


								    # this sorts the %age hash by value instead of key

								    # using an in-line function

								    @eldest = sort { $age{$b} <=> $age{$a} } keys %age;


								    # sort using explicit subroutine name

								    sub byage {

									$age{$a} <=> $age{$b};	# presuming numeric

								    }

								    @sortedclass = sort byage @class;


								    sub backwards { $b cmp $a }

								    @harry  = qw(dog cat x Cain Abel);

								    @george = qw(gone chased yz Punished Axed);

								    print sort @harry;

									    # prints AbelCaincatdogx

								    print sort backwards @harry;

									    # prints xdogcatCainAbel

								    print sort @george, 'to', @harry;

									    # prints AbelAxedCainPunishedcatchaseddoggonetoxyz


								    # inefficiently sort by descending numeric compare using

								    # the first integer after the first = sign, or the

								    # whole record case-insensitively otherwise


								    @new = sort {

									($b =~ /=(\d+)/)[0] <=> ($a =~ /=(\d+)/)[0]

											    ||

									            uc($a)  cmp  uc($b)

								    } @old;


								    # same thing, but much more efficiently;

								    # we'll build auxiliary indices instead

								    # for speed

								    @nums = @caps = ();

								    for (@old) {

									push @nums, /=(\d+)/;

									push @caps, uc($_);

								    }


								    @new = @old[ sort {

											$nums[$b] <=> $nums[$a]

												 ||

											$caps[$a] cmp $caps[$b]

										       } 0..$#old

									       ];


								    # same thing, but without any temps

								    @new = map { $_->[0] }

								           sort { $b->[1] <=> $a->[1]

								                           ||

								                  $a->[2] cmp $b->[2]

								           } map { [$_, /=(\d+)/, uc($_)] } @old;


								    # using a prototype allows you to use any comparison subroutine

								    # as a sort subroutine (including other package's subroutines)

								    package other;

								    sub backwards ($$) { $_[1] cmp $_[0]; }	# $a and $b are not set here


								    package main;

								    @new = sort other::backwards @old;


								If you're using strict, you I<must not> declare $a

								and $b as lexicals.  They are package globals.  That means

								if you're in the C<main> package and type


								    @articles = sort {$b <=> $a} @files;


								then C<$a> and C<$b> are C<$main::a> and C<$main::b> (or C<$::a> and C<$::b>),

								but if you're in the C<FooPack> package, it's the same as typing


								    @articles = sort {$FooPack::b <=> $FooPack::a} @files;


								The comparison function is required to behave.  If it returns

								inconsistent results (sometimes saying C<$x[1]> is less than C<$x[2]> and

								sometimes saying the opposite, for example) the results are not

								well-defined.


								=item splice ARRAY,OFFSET,LENGTH,LIST


								=item splice ARRAY,OFFSET,LENGTH


								=item splice ARRAY,OFFSET


								=item splice ARRAY


								Removes the elements designated by OFFSET and LENGTH from an array, and

								replaces them with the elements of LIST, if any.  In list context,

								returns the elements removed from the array.  In scalar context,

								returns the last element removed, or C<undef> if no elements are

								removed.  The array grows or shrinks as necessary.

								If OFFSET is negative then it starts that far from the end of the array.

								If LENGTH is omitted, removes everything from OFFSET onward.

								If LENGTH is negative, leaves that many elements off the end of the array.

								If both OFFSET and LENGTH are omitted, removes everything.


								The following equivalences hold (assuming C<$[ == 0>):


								    push(@a,$x,$y)	splice(@a,@a,0,$x,$y)

								    pop(@a)		splice(@a,-1)

								    shift(@a)		splice(@a,0,1)

								    unshift(@a,$x,$y)	splice(@a,0,0,$x,$y)

								    $a[$x] = $y		splice(@a,$x,1,$y)


								Example, assuming array lengths are passed before arrays:


								    sub aeq {	# compare two list values

									my(@a) = splice(@_,0,shift);

									my(@b) = splice(@_,0,shift);

									return 0 unless @a == @b;	# same len?

									while (@a) {

									    return 0 if pop(@a) ne pop(@b);

									}

									return 1;

								    }

								    if (&aeq($len,@foo[1..$len],0+@bar,@bar)) { ... }


								=item split /PATTERN/,EXPR,LIMIT


								=item split /PATTERN/,EXPR


								=item split /PATTERN/


								=item split


								Splits a string into a list of strings and returns that list.  By default,

								empty leading fields are preserved, and empty trailing ones are deleted.


								In scalar context, returns the number of fields found and splits into

								the C<@_> array.  Use of split in scalar context is deprecated, however,

								because it clobbers your subroutine arguments.


								If EXPR is omitted, splits the C<$_> string.  If PATTERN is also omitted,

								splits on whitespace (after skipping any leading whitespace).  Anything

								matching PATTERN is taken to be a delimiter separating the fields.  (Note

								that the delimiter may be longer than one character.)


								If LIMIT is specified and positive, splits into no more than that

								many fields (though it may split into fewer).  If LIMIT is unspecified

								or zero, trailing null fields are stripped (which potential users

								of C<pop> would do well to remember).  If LIMIT is negative, it is

								treated as if an arbitrarily large LIMIT had been specified.


								A pattern matching the null string (not to be confused with

								a null pattern C<//>, which is just one member of the set of patterns

								matching a null string) will split the value of EXPR into separate

								characters at each point it matches that way.  For example:


								    print join(':', split(/ */, 'hi there'));


								produces the output 'h:i:t:h:e:r:e'.


								Empty leading (or trailing) fields are produced when there positive width

								matches at the beginning (or end) of the string; a zero-width match at the

								beginning (or end) of the string does not produce an empty field.  For

								example:


								   print join(':', split(/(?=\w)/, 'hi there!'));


								produces the output 'h:i :t:h:e:r:e!'.


								The LIMIT parameter can be used to split a line partially


								    ($login, $passwd, $remainder) = split(/:/, $_, 3);


								When assigning to a list, if LIMIT is omitted, Perl supplies a LIMIT

								one larger than the number of variables in the list, to avoid

								unnecessary work.  For the list above LIMIT would have been 4 by

								default.  In time critical applications it behooves you not to split

								into more fields than you really need.


								If the PATTERN contains parentheses, additional list elements are

								created from each matching substring in the delimiter.


								    split(/([,-])/, "1-10,20", 3);


								produces the list value


								    (1, '-', 10, ',', 20)


								If you had the entire header of a normal Unix email message in $header,

								you could split it up into fields and their values this way:


								    $header =~ s/\n\s+/ /g;  # fix continuation lines

								    %hdrs   =  (UNIX_FROM => split /^(\S*?):\s*/m, $header);


								The pattern C</PATTERN/> may be replaced with an expression to specify

								patterns that vary at runtime.  (To do runtime compilation only once,

								use C</$variable/o>.)


								As a special case, specifying a PATTERN of space (C<' '>) will split on

								white space just as C<split> with no arguments does.  Thus, C<split(' ')> can

								be used to emulate B<awk>'s default behavior, whereas C<split(/ /)>

								will give you as many null initial fields as there are leading spaces.

								A C<split> on C</\s+/> is like a C<split(' ')> except that any leading

								whitespace produces a null first field.  A C<split> with no arguments

								really does a C<split(' ', $_)> internally.


								A PATTERN of C</^/> is treated as if it were C</^/m>, since it isn't

								much use otherwise.


								Example:


								    open(PASSWD, '/etc/passwd');

								    while (<PASSWD>) {

								        chomp;

								        ($login, $passwd, $uid, $gid,

								         $gcos, $home, $shell) = split(/:/);

									#...

								    }


								=item sprintf FORMAT, LIST


								Returns a string formatted by the usual C<printf> conventions of the C

								library function C<sprintf>.  See below for more details

								and see L<sprintf(3)> or L<printf(3)> on your system for an explanation of

								the general principles.


								For example:


								        # Format number with up to 8 leading zeroes

								        $result = sprintf("%08d", $number);


								        # Round number to 3 digits after decimal point

								        $rounded = sprintf("%.3f", $number);


								Perl does its own C<sprintf> formatting--it emulates the C

								function C<sprintf>, but it doesn't use it (except for floating-point

								numbers, and even then only the standard modifiers are allowed).  As a

								result, any non-standard extensions in your local C<sprintf> are not

								available from Perl.


								Unlike C<printf>, C<sprintf> does not do what you probably mean when you

								pass it an array as your first argument. The array is given scalar context,

								and instead of using the 0th element of the array as the format, Perl will

								use the count of elements in the array as the format, which is almost never

								useful.


								Perl's C<sprintf> permits the following universally-known conversions:


								   %%	a percent sign

								   %c	a character with the given number

								   %s	a string

								   %d	a signed integer, in decimal

								   %u	an unsigned integer, in decimal

								   %o	an unsigned integer, in octal

								   %x	an unsigned integer, in hexadecimal

								   %e	a floating-point number, in scientific notation

								   %f	a floating-point number, in fixed decimal notation

								   %g	a floating-point number, in %e or %f notation


								In addition, Perl permits the following widely-supported conversions:


								   %X	like %x, but using upper-case letters

								   %E	like %e, but using an upper-case "E"

								   %G	like %g, but with an upper-case "E" (if applicable)

								   %b	an unsigned integer, in binary

								   %p	a pointer (outputs the Perl value's address in hexadecimal)

								   %n	special: *stores* the number of characters output so far

								        into the next variable in the parameter list


								Finally, for backward (and we do mean "backward") compatibility, Perl

								permits these unnecessary but widely-supported conversions:


								   %i	a synonym for %d

								   %D	a synonym for %ld

								   %U	a synonym for %lu

								   %O	a synonym for %lo

								   %F	a synonym for %f


								Note that the number of exponent digits in the scientific notation by

								C<%e>, C<%E>, C<%g> and C<%G> for numbers with the modulus of the

								exponent less than 100 is system-dependent: it may be three or less

								(zero-padded as necessary).  In other words, 1.23 times ten to the

								99th may be either "1.23e99" or "1.23e099".


								Perl permits the following universally-known flags between the C<%>

								and the conversion letter:


								   space   prefix positive number with a space

								   +       prefix positive number with a plus sign

								   -       left-justify within the field

								   0       use zeros, not spaces, to right-justify

								   #       prefix non-zero octal with "0", non-zero hex with "0x"

								   number  minimum field width

								   .number "precision": digits after decimal point for

								           floating-point, max length for string, minimum length

								           for integer

								   l       interpret integer as C type "long" or "unsigned long"

								   h       interpret integer as C type "short" or "unsigned short"

								           If no flags, interpret integer as C type "int" or "unsigned"


								There are also two Perl-specific flags:


								   V       interpret integer as Perl's standard integer type

								   v       interpret string as a vector of integers, output as

								           numbers separated either by dots, or by an arbitrary

									   string received from the argument list when the flag

									   is preceded by C<*>


								Where a number would appear in the flags, an asterisk (C<*>) may be

								used instead, in which case Perl uses the next item in the parameter

								list as the given number (that is, as the field width or precision).

								If a field width obtained through C<*> is negative, it has the same

								effect as the C<-> flag: left-justification.


								The C<v> flag is useful for displaying ordinal values of characters

								in arbitrary strings:


								    printf "version is v%vd\n", $^V;		# Perl's version

								    printf "address is %*vX\n", ":", $addr;	# IPv6 address

								    printf "bits are %*vb\n", " ", $bits;	# random bitstring


								If C<use locale> is in effect, the character used for the decimal

								point in formatted real numbers is affected by the LC_NUMERIC locale.

								See L<perllocale>.


								If Perl understands "quads" (64-bit integers) (this requires

								either that the platform natively support quads or that Perl

								be specifically compiled to support quads), the characters


									d u o x X b i D U O


								print quads, and they may optionally be preceded by


									ll L q


								For example


									%lld %16LX %qo


								You can find out whether your Perl supports quads via L<Config>:


									use Config;

									($Config{use64bitint} eq 'define' || $Config{longsize} == 8) &&

										print "quads\n";


								If Perl understands "long doubles" (this requires that the platform

								support long doubles), the flags


									e f g E F G


								may optionally be preceded by


									ll L


								For example


									%llf %Lg


								You can find out whether your Perl supports long doubles via L<Config>:


									use Config;

									$Config{d_longdbl} eq 'define' && print "long doubles\n";


								=item sqrt EXPR


								=item sqrt


								Return the square root of EXPR.  If EXPR is omitted, returns square

								root of C<$_>.  Only works on non-negative operands, unless you've

								loaded the standard Math::Complex module.


								    use Math::Complex;

								    print sqrt(-2);    # prints 1.4142135623731i


								=item srand EXPR


								=item srand


								Sets the random number seed for the C<rand> operator.  If EXPR is

								omitted, uses a semi-random value supplied by the kernel (if it supports

								the F</dev/urandom> device) or based on the current time and process

								ID, among other things.  In versions of Perl prior to 5.004 the default

								seed was just the current C<time>.  This isn't a particularly good seed,

								so many old programs supply their own seed value (often C<time ^ $$> or

								C<time ^ ($$ + ($$ << 15))>), but that isn't necessary any more.


								In fact, it's usually not necessary to call C<srand> at all, because if

								it is not called explicitly, it is called implicitly at the first use of

								the C<rand> operator.  However, this was not the case in version of Perl

								before 5.004, so if your script will run under older Perl versions, it

								should call C<srand>.


								Note that you need something much more random than the default seed for

								cryptographic purposes.  Checksumming the compressed output of one or more

								rapidly changing operating system status programs is the usual method.  For

								example:


								    srand (time ^ $$ ^ unpack "%L*", `ps axww | gzip`);


								If you're particularly concerned with this, see the C<Math::TrulyRandom>

								module in CPAN.


								Do I<not> call C<srand> multiple times in your program unless you know

								exactly what you're doing and why you're doing it.  The point of the

								function is to "seed" the C<rand> function so that C<rand> can produce

								a different sequence each time you run your program.  Just do it once at the

								top of your program, or you I<won't> get random numbers out of C<rand>!


								Frequently called programs (like CGI scripts) that simply use


								    time ^ $$


								for a seed can fall prey to the mathematical property that


								    a^b == (a+1)^(b+1)


								one-third of the time.  So don't do that.


								=item stat FILEHANDLE


								=item stat EXPR


								=item stat


								Returns a 13-element list giving the status info for a file, either

								the file opened via FILEHANDLE, or named by EXPR.  If EXPR is omitted,

								it stats C<$_>.  Returns a null list if the stat fails.  Typically used

								as follows:


								    ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,

								       $atime,$mtime,$ctime,$blksize,$blocks)

								           = stat($filename);


								Not all fields are supported on all filesystem types.  Here are the

								meaning of the fields:


								  0 dev      device number of filesystem

								  1 ino      inode number

								  2 mode     file mode  (type and permissions)

								  3 nlink    number of (hard) links to the file

								  4 uid      numeric user ID of file's owner

								  5 gid      numeric group ID of file's owner

								  6 rdev     the device identifier (special files only)

								  7 size     total size of file, in bytes

								  8 atime    last access time in seconds since the epoch

								  9 mtime    last modify time in seconds since the epoch

								 10 ctime    inode change time (NOT creation time!) in seconds since the epoch

								 11 blksize  preferred block size for file system I/O

								 12 blocks   actual number of blocks allocated


								(The epoch was at 00:00 January 1, 1970 GMT.)


								If stat is passed the special filehandle consisting of an underline, no

								stat is done, but the current contents of the stat structure from the

								last stat or filetest are returned.  Example:


								    if (-x $file && (($d) = stat(_)) && $d < 0) {

									print "$file is executable NFS file\n";

								    }


								(This works on machines only for which the device number is negative

								under NFS.)


								Because the mode contains both the file type and its permissions, you

								should mask off the file type portion and (s)printf using a C<"%o">

								if you want to see the real permissions.


								    $mode = (stat($filename))[2];

								    printf "Permissions are %04o\n", $mode & 07777;


								In scalar context, C<stat> returns a boolean value indicating success

								or failure, and, if successful, sets the information associated with

								the special filehandle C<_>.


								The File::stat module provides a convenient, by-name access mechanism:


								    use File::stat;

								    $sb = stat($filename);

								    printf "File is %s, size is %s, perm %04o, mtime %s\n",

									$filename, $sb->size, $sb->mode & 07777,

									scalar localtime $sb->mtime;


								You can import symbolic mode constants (C<S_IF*>) and functions

								(C<S_IS*>) from the Fcntl module:


								    use Fcntl ':mode';


								    $mode = (stat($filename))[2];


								    $user_rwx      = ($mode & S_IRWXU) >> 6;

								    $group_read    = ($mode & S_IRGRP) >> 3;

								    $other_execute =  $mode & S_IXOTH;


								    printf "Permissions are %04o\n", S_ISMODE($mode), "\n";


								    $is_setuid     =  $mode & S_ISUID;

								    $is_setgid     =  S_ISDIR($mode);


								You could write the last two using the C<-u> and C<-d> operators.

								The commonly available S_IF* constants are


								    # Permissions: read, write, execute, for user, group, others.


								    S_IRWXU S_IRUSR S_IWUSR S_IXUSR

								    S_IRWXG S_IRGRP S_IWGRP S_IXGRP

								    S_IRWXO S_IROTH S_IWOTH S_IXOTH


								    # Setuid/Setgid/Stickiness.


								    S_ISUID S_ISGID S_ISVTX S_ISTXT


								    # File types.  Not necessarily all are available on your system.


								    S_IFREG S_IFDIR S_IFLNK S_IFBLK S_ISCHR S_IFIFO S_IFSOCK S_IFWHT S_ENFMT


								    # The following are compatibility aliases for S_IRUSR, S_IWUSR, S_IXUSR.


								    S_IREAD S_IWRITE S_IEXEC


								and the S_IF* functions are


								    S_IFMODE($mode)	the part of $mode containing the permission bits

											and the setuid/setgid/sticky bits


								    S_IFMT($mode)	the part of $mode containing the file type

											which can be bit-anded with e.g. S_IFREG

								                        or with the following functions


								    # The operators -f, -d, -l, -b, -c, -p, and -s.


								    S_ISREG($mode) S_ISDIR($mode) S_ISLNK($mode)

								    S_ISBLK($mode) S_ISCHR($mode) S_ISFIFO($mode) S_ISSOCK($mode)


								    # No direct -X operator counterpart, but for the first one

								    # the -g operator is often equivalent.  The ENFMT stands for

								    # record flocking enforcement, a platform-dependent feature.


								    S_ISENFMT($mode) S_ISWHT($mode)


								See your native chmod(2) and stat(2) documentation for more details

								about the S_* constants.


								=item study SCALAR


								=item study


								Takes extra time to study SCALAR (C<$_> if unspecified) in anticipation of

								doing many pattern matches on the string before it is next modified.

								This may or may not save time, depending on the nature and number of

								patterns you are searching on, and on the distribution of character

								frequencies in the string to be searched--you probably want to compare

								run times with and without it to see which runs faster.  Those loops

								which scan for many short constant strings (including the constant

								parts of more complex patterns) will benefit most.  You may have only

								one C<study> active at a time--if you study a different scalar the first

								is "unstudied".  (The way C<study> works is this: a linked list of every

								character in the string to be searched is made, so we know, for

								example, where all the C<'k'> characters are.  From each search string,

								the rarest character is selected, based on some static frequency tables

								constructed from some C programs and English text.  Only those places

								that contain this "rarest" character are examined.)


								For example, here is a loop that inserts index producing entries

								before any line containing a certain pattern:


								    while (<>) {

									study;

									print ".IX foo\n" 	if /\bfoo\b/;

									print ".IX bar\n" 	if /\bbar\b/;

									print ".IX blurfl\n" 	if /\bblurfl\b/;

									# ...

									print;

								    }


								In searching for C</\bfoo\b/>, only those locations in C<$_> that contain C<f>

								will be looked at, because C<f> is rarer than C<o>.  In general, this is

								a big win except in pathological cases.  The only question is whether

								it saves you more time than it took to build the linked list in the

								first place.


								Note that if you have to look for strings that you don't know till

								runtime, you can build an entire loop as a string and C<eval> that to

								avoid recompiling all your patterns all the time.  Together with

								undefining C<$/> to input entire files as one record, this can be very

								fast, often faster than specialized programs like fgrep(1).  The following

								scans a list of files (C<@files>) for a list of words (C<@words>), and prints

								out the names of those files that contain a match:


								    $search = 'while (<>) { study;';

								    foreach $word (@words) {

									$search .= "++\$seen{\$ARGV} if /\\b$word\\b/;\n";

								    }

								    $search .= "}";

								    @ARGV = @files;

								    undef $/;

								    eval $search;		# this screams

								    $/ = "\n";		# put back to normal input delimiter

								    foreach $file (sort keys(%seen)) {

									print $file, "\n";

								    }


								=item sub BLOCK


								=item sub NAME


								=item sub NAME BLOCK


								This is subroutine definition, not a real function I<per se>.  With just a

								NAME (and possibly prototypes or attributes), it's just a forward declaration.

								Without a NAME, it's an anonymous function declaration, and does actually

								return a value: the CODE ref of the closure you just created.  See L<perlsub>

								and L<perlref> for details.


								=item substr EXPR,OFFSET,LENGTH,REPLACEMENT


								=item substr EXPR,OFFSET,LENGTH


								=item substr EXPR,OFFSET


								Extracts a substring out of EXPR and returns it.  First character is at

								offset C<0>, or whatever you've set C<$[> to (but don't do that).

								If OFFSET is negative (or more precisely, less than C<$[>), starts

								that far from the end of the string.  If LENGTH is omitted, returns

								everything to the end of the string.  If LENGTH is negative, leaves that

								many characters off the end of the string.


								You can use the substr() function as an lvalue, in which case EXPR

								must itself be an lvalue.  If you assign something shorter than LENGTH,

								the string will shrink, and if you assign something longer than LENGTH,

								the string will grow to accommodate it.  To keep the string the same

								length you may need to pad or chop your value using C<sprintf>.


								If OFFSET and LENGTH specify a substring that is partly outside the

								string, only the part within the string is returned.  If the substring

								is beyond either end of the string, substr() returns the undefined

								value and produces a warning.  When used as an lvalue, specifying a

								substring that is entirely outside the string is a fatal error.

								Here's an example showing the behavior for boundary cases:


								    my $name = 'fred';

								    substr($name, 4) = 'dy';		# $name is now 'freddy'

								    my $null = substr $name, 6, 2;	# returns '' (no warning)

								    my $oops = substr $name, 7;		# returns undef, with warning

								    substr($name, 7) = 'gap';		# fatal error


								An alternative to using substr() as an lvalue is to specify the

								replacement string as the 4th argument.  This allows you to replace

								parts of the EXPR and return what was there before in one operation,

								just as you can with splice().


								=item symlink OLDFILE,NEWFILE


								Creates a new filename symbolically linked to the old filename.

								Returns C<1> for success, C<0> otherwise.  On systems that don't support

								symbolic links, produces a fatal error at run time.  To check for that,

								use eval:


								    $symlink_exists = eval { symlink("",""); 1 };


								=item syscall LIST


								Calls the system call specified as the first element of the list,

								passing the remaining elements as arguments to the system call.  If

								unimplemented, produces a fatal error.  The arguments are interpreted

								as follows: if a given argument is numeric, the argument is passed as

								an int.  If not, the pointer to the string value is passed.  You are

								responsible to make sure a string is pre-extended long enough to

								receive any result that might be written into a string.  You can't use a

								string literal (or other read-only string) as an argument to C<syscall>

								because Perl has to assume that any string pointer might be written

								through.  If your

								integer arguments are not literals and have never been interpreted in a

								numeric context, you may need to add C<0> to them to force them to look

								like numbers.  This emulates the C<syswrite> function (or vice versa):


								    require 'syscall.ph';		# may need to run h2ph

								    $s = "hi there\n";

								    syscall(&SYS_write, fileno(STDOUT), $s, length $s);


								Note that Perl supports passing of up to only 14 arguments to your system call,

								which in practice should usually suffice.


								Syscall returns whatever value returned by the system call it calls.

								If the system call fails, C<syscall> returns C<-1> and sets C<$!> (errno).

								Note that some system calls can legitimately return C<-1>.  The proper

								way to handle such calls is to assign C<$!=0;> before the call and

								check the value of C<$!> if syscall returns C<-1>.


								There's a problem with C<syscall(&SYS_pipe)>: it returns the file

								number of the read end of the pipe it creates.  There is no way

								to retrieve the file number of the other end.  You can avoid this

								problem by using C<pipe> instead.


								=item sysopen FILEHANDLE,FILENAME,MODE


								=item sysopen FILEHANDLE,FILENAME,MODE,PERMS


								Opens the file whose filename is given by FILENAME, and associates it

								with FILEHANDLE.  If FILEHANDLE is an expression, its value is used as

								the name of the real filehandle wanted.  This function calls the

								underlying operating system's C<open> function with the parameters

								FILENAME, MODE, PERMS.


								The possible values and flag bits of the MODE parameter are

								system-dependent; they are available via the standard module C<Fcntl>.

								See the documentation of your operating system's C<open> to see which

								values and flag bits are available.  You may combine several flags

								using the C<|>-operator.


								Some of the most common values are C<O_RDONLY> for opening the file in

								read-only mode, C<O_WRONLY> for opening the file in write-only mode,

								and C<O_RDWR> for opening the file in read-write mode, and.


								For historical reasons, some values work on almost every system

								supported by perl: zero means read-only, one means write-only, and two

								means read/write.  We know that these values do I<not> work under

								OS/390 & VM/ESA Unix and on the Macintosh; you probably don't want to

								use them in new code.


								If the file named by FILENAME does not exist and the C<open> call creates

								it (typically because MODE includes the C<O_CREAT> flag), then the value of

								PERMS specifies the permissions of the newly created file.  If you omit

								the PERMS argument to C<sysopen>, Perl uses the octal value C<0666>.

								These permission values need to be in octal, and are modified by your

								process's current C<umask>.


								In many systems the C<O_EXCL> flag is available for opening files in

								exclusive mode.  This is B<not> locking: exclusiveness means here that

								if the file already exists, sysopen() fails.  The C<O_EXCL> wins

								C<O_TRUNC>.


								Sometimes you may want to truncate an already-existing file: C<O_TRUNC>.


								You should seldom if ever use C<0644> as argument to C<sysopen>, because

								that takes away the user's option to have a more permissive umask.

								Better to omit it.  See the perlfunc(1) entry on C<umask> for more

								on this.


								Note that C<sysopen> depends on the fdopen() C library function.

								On many UNIX systems, fdopen() is known to fail when file descriptors

								exceed a certain value, typically 255. If you need more file

								descriptors than that, consider rebuilding Perl to use the C<sfio>

								library, or perhaps using the POSIX::open() function.


								See L<perlopentut> for a kinder, gentler explanation of opening files.


								=item sysread FILEHANDLE,SCALAR,LENGTH,OFFSET


								=item sysread FILEHANDLE,SCALAR,LENGTH


								Attempts to read LENGTH bytes of data into variable SCALAR from the

								specified FILEHANDLE, using the system call read(2).  It bypasses stdio,

								so mixing this with other kinds of reads, C<print>, C<write>,

								C<seek>, C<tell>, or C<eof> can cause confusion because stdio

								usually buffers data.  Returns the number of bytes actually read, C<0>

								at end of file, or undef if there was an error.  SCALAR will be grown or

								shrunk so that the last byte actually read is the last byte of the

								scalar after the read.


								An OFFSET may be specified to place the read data at some place in the

								string other than the beginning.  A negative OFFSET specifies

								placement at that many bytes counting backwards from the end of the

								string.  A positive OFFSET greater than the length of SCALAR results

								in the string being padded to the required size with C<"\0"> bytes before

								the result of the read is appended.


								There is no syseof() function, which is ok, since eof() doesn't work

								very well on device files (like ttys) anyway.  Use sysread() and check

								for a return value for 0 to decide whether you're done.


								=item sysseek FILEHANDLE,POSITION,WHENCE


								Sets FILEHANDLE's system position using the system call lseek(2).  It

								bypasses stdio, so mixing this with reads (other than C<sysread>),

								C<print>, C<write>, C<seek>, C<tell>, or C<eof> may cause confusion.

								FILEHANDLE may be an expression whose value gives the name of the

								filehandle.  The values for WHENCE are C<0> to set the new position to

								POSITION, C<1> to set the it to the current position plus POSITION,

								and C<2> to set it to EOF plus POSITION (typically negative).  For

								WHENCE, you may also use the constants C<SEEK_SET>, C<SEEK_CUR>, and

								C<SEEK_END> (start of the file, current position, end of the file)

								from the Fcntl module.


								Returns the new position, or the undefined value on failure.  A position

								of zero is returned as the string C<"0 but true">; thus C<sysseek> returns

								true on success and false on failure, yet you can still easily determine

								the new position.


								=item system LIST


								=item system PROGRAM LIST


								Does exactly the same thing as C<exec LIST>, except that a fork is

								done first, and the parent process waits for the child process to

								complete.  Note that argument processing varies depending on the

								number of arguments.  If there is more than one argument in LIST,

								or if LIST is an array with more than one value, starts the program

								given by the first element of the list with arguments given by the

								rest of the list.  If there is only one scalar argument, the argument

								is checked for shell metacharacters, and if there are any, the

								entire argument is passed to the system's command shell for parsing

								(this is C</bin/sh -c> on Unix platforms, but varies on other

								platforms).  If there are no shell metacharacters in the argument,

								it is split into words and passed directly to C<execvp>, which is

								more efficient.


								Beginning with v5.6.0, Perl will attempt to flush all files opened for

								output before any operation that may do a fork, but this may not be

								supported on some platforms (see L<perlport>).  To be safe, you may need

								to set C<$|> ($AUTOFLUSH in English) or call the C<autoflush()> method

								of C<IO::Handle> on any open handles.


								The return value is the exit status of the program as

								returned by the C<wait> call.  To get the actual exit value divide by

								256.  See also L</exec>.  This is I<not> what you want to use to capture

								the output from a command, for that you should use merely backticks or

								C<qx//>, as described in L<perlop/"`STRING`">.  Return value of -1

								indicates a failure to start the program (inspect $! for the reason).


								Like C<exec>, C<system> allows you to lie to a program about its name if

								you use the C<system PROGRAM LIST> syntax.  Again, see L</exec>.


								Because C<system> and backticks block C<SIGINT> and C<SIGQUIT>, killing the

								program they're running doesn't actually interrupt your program.


								    @args = ("command", "arg1", "arg2");

								    system(@args) == 0

									 or die "system @args failed: $?"


								You can check all the failure possibilities by inspecting

								C<$?> like this:


								    $exit_value  = $? >> 8;

								    $signal_num  = $? & 127;

								    $dumped_core = $? & 128;


								When the arguments get executed via the system shell, results

								and return codes will be subject to its quirks and capabilities.

								See L<perlop/"`STRING`"> and L</exec> for details.


								=item syswrite FILEHANDLE,SCALAR,LENGTH,OFFSET


								=item syswrite FILEHANDLE,SCALAR,LENGTH


								=item syswrite FILEHANDLE,SCALAR


								Attempts to write LENGTH bytes of data from variable SCALAR to the

								specified FILEHANDLE, using the system call write(2).  If LENGTH

								is not specified, writes whole SCALAR.  It bypasses stdio, so mixing

								this with reads (other than C<sysread())>, C<print>, C<write>,

								C<seek>, C<tell>, or C<eof> may cause confusion because stdio

								usually buffers data.  Returns the number of bytes actually written,

								or C<undef> if there was an error.  If the LENGTH is greater than

								the available data in the SCALAR after the OFFSET, only as much

								data as is available will be written.


								An OFFSET may be specified to write the data from some part of the

								string other than the beginning.  A negative OFFSET specifies writing

								that many bytes counting backwards from the end of the string.  In the

								case the SCALAR is empty you can use OFFSET but only zero offset.


								=item tell FILEHANDLE


								=item tell


								Returns the current position for FILEHANDLE, or -1 on error.  FILEHANDLE

								may be an expression whose value gives the name of the actual filehandle.

								If FILEHANDLE is omitted, assumes the file last read.


								The return value of tell() for the standard streams like the STDIN

								depends on the operating system: it may return -1 or something else.

								tell() on pipes, fifos, and sockets usually returns -1.


								There is no C<systell> function.  Use C<sysseek(FH, 0, 1)> for that.


								=item telldir DIRHANDLE


								Returns the current position of the C<readdir> routines on DIRHANDLE.

								Value may be given to C<seekdir> to access a particular location in a

								directory.  Has the same caveats about possible directory compaction as

								the corresponding system library routine.


								=item tie VARIABLE,CLASSNAME,LIST


								This function binds a variable to a package class that will provide the

								implementation for the variable.  VARIABLE is the name of the variable

								to be enchanted.  CLASSNAME is the name of a class implementing objects

								of correct type.  Any additional arguments are passed to the C<new>

								method of the class (meaning C<TIESCALAR>, C<TIEHANDLE>, C<TIEARRAY>,

								or C<TIEHASH>).  Typically these are arguments such as might be passed

								to the C<dbm_open()> function of C.  The object returned by the C<new>

								method is also returned by the C<tie> function, which would be useful

								if you want to access other methods in CLASSNAME.


								Note that functions such as C<keys> and C<values> may return huge lists

								when used on large objects, like DBM files.  You may prefer to use the

								C<each> function to iterate over such.  Example:


								    # print out history file offsets

								    use NDBM_File;

								    tie(%HIST, 'NDBM_File', '/usr/lib/news/history', 1, 0);

								    while (($key,$val) = each %HIST) {

									print $key, ' = ', unpack('L',$val), "\n";

								    }

								    untie(%HIST);


								A class implementing a hash should have the following methods:


								    TIEHASH classname, LIST

								    FETCH this, key

								    STORE this, key, value

								    DELETE this, key

								    CLEAR this

								    EXISTS this, key

								    FIRSTKEY this

								    NEXTKEY this, lastkey

								    DESTROY this

								    UNTIE this


								A class implementing an ordinary array should have the following methods:


								    TIEARRAY classname, LIST

								    FETCH this, key

								    STORE this, key, value

								    FETCHSIZE this

								    STORESIZE this, count

								    CLEAR this

								    PUSH this, LIST

								    POP this

								    SHIFT this

								    UNSHIFT this, LIST

								    SPLICE this, offset, length, LIST

								    EXTEND this, count

								    DESTROY this

								    UNTIE this


								A class implementing a file handle should have the following methods:


								    TIEHANDLE classname, LIST

								    READ this, scalar, length, offset

								    READLINE this

								    GETC this

								    WRITE this, scalar, length, offset

								    PRINT this, LIST

								    PRINTF this, format, LIST

								    BINMODE this

								    EOF this

								    FILENO this

								    SEEK this, position, whence

								    TELL this

								    OPEN this, mode, LIST

								    CLOSE this

								    DESTROY this

								    UNTIE this


								A class implementing a scalar should have the following methods:


								    TIESCALAR classname, LIST

								    FETCH this,

								    STORE this, value

								    DESTROY this

								    UNTIE this


								Not all methods indicated above need be implemented.  See L<perltie>,

								L<Tie::Hash>, L<Tie::Array>, L<Tie::Scalar>, and L<Tie::Handle>.


								Unlike C<dbmopen>, the C<tie> function will not use or require a module

								for you--you need to do that explicitly yourself.  See L<DB_File>

								or the F<Config> module for interesting C<tie> implementations.


								For further details see L<perltie>, L<"tied VARIABLE">.


								=item tied VARIABLE


								Returns a reference to the object underlying VARIABLE (the same value

								that was originally returned by the C<tie> call that bound the variable

								to a package.)  Returns the undefined value if VARIABLE isn't tied to a

								package.


								=item time


								Returns the number of non-leap seconds since whatever time the system

								considers to be the epoch (that's 00:00:00, January 1, 1904 for MacOS,

								and 00:00:00 UTC, January 1, 1970 for most other systems).

								Suitable for feeding to C<gmtime> and C<localtime>.


								For measuring time in better granularity than one second,

								you may use either the Time::HiRes module from CPAN, or

								if you have gettimeofday(2), you may be able to use the

								C<syscall> interface of Perl, see L<perlfaq8> for details.


								=item times


								Returns a four-element list giving the user and system times, in

								seconds, for this process and the children of this process.


								    ($user,$system,$cuser,$csystem) = times;


								=item tr///


								The transliteration operator.  Same as C<y///>.  See L<perlop>.


								=item truncate FILEHANDLE,LENGTH


								=item truncate EXPR,LENGTH


								Truncates the file opened on FILEHANDLE, or named by EXPR, to the

								specified length.  Produces a fatal error if truncate isn't implemented

								on your system.  Returns true if successful, the undefined value

								otherwise.


								=item uc EXPR


								=item uc


								Returns an uppercased version of EXPR.  This is the internal function

								implementing the C<\U> escape in double-quoted strings.

								Respects current LC_CTYPE locale if C<use locale> in force.  See L<perllocale>.

								Under Unicode (C<use utf8>) it uses the standard Unicode uppercase mappings.  (It

								does not attempt to do titlecase mapping on initial letters.  See C<ucfirst> for that.)


								If EXPR is omitted, uses C<$_>.


								=item ucfirst EXPR


								=item ucfirst


								Returns the value of EXPR with the first character

								in uppercase (titlecase in Unicode).  This is

								the internal function implementing the C<\u> escape in double-quoted strings.

								Respects current LC_CTYPE locale if C<use locale> in force.  See L<perllocale>

								and L<utf8>.


								If EXPR is omitted, uses C<$_>.


								=item umask EXPR


								=item umask


								Sets the umask for the process to EXPR and returns the previous value.

								If EXPR is omitted, merely returns the current umask.


								The Unix permission C<rwxr-x---> is represented as three sets of three

								bits, or three octal digits: C<0750> (the leading 0 indicates octal

								and isn't one of the digits).  The C<umask> value is such a number

								representing disabled permissions bits.  The permission (or "mode")

								values you pass C<mkdir> or C<sysopen> are modified by your umask, so

								even if you tell C<sysopen> to create a file with permissions C<0777>,

								if your umask is C<0022> then the file will actually be created with

								permissions C<0755>.  If your C<umask> were C<0027> (group can't

								write; others can't read, write, or execute), then passing

								C<sysopen> C<0666> would create a file with mode C<0640> (C<0666 &~

								027> is C<0640>).


								Here's some advice: supply a creation mode of C<0666> for regular

								files (in C<sysopen>) and one of C<0777> for directories (in

								C<mkdir>) and executable files.  This gives users the freedom of

								choice: if they want protected files, they might choose process umasks

								of C<022>, C<027>, or even the particularly antisocial mask of C<077>.

								Programs should rarely if ever make policy decisions better left to

								the user.  The exception to this is when writing files that should be

								kept private: mail files, web browser cookies, I<.rhosts> files, and

								so on.


								If umask(2) is not implemented on your system and you are trying to

								restrict access for I<yourself> (i.e., (EXPR & 0700) > 0), produces a

								fatal error at run time.  If umask(2) is not implemented and you are

								not trying to restrict access for yourself, returns C<undef>.


								Remember that a umask is a number, usually given in octal; it is I<not> a

								string of octal digits.  See also L</oct>, if all you have is a string.


								=item undef EXPR


								=item undef


								Undefines the value of EXPR, which must be an lvalue.  Use only on a

								scalar value, an array (using C<@>), a hash (using C<%>), a subroutine

								(using C<&>), or a typeglob (using <*>).  (Saying C<undef $hash{$key}>

								will probably not do what you expect on most predefined variables or

								DBM list values, so don't do that; see L<delete>.)  Always returns the

								undefined value.  You can omit the EXPR, in which case nothing is

								undefined, but you still get an undefined value that you could, for

								instance, return from a subroutine, assign to a variable or pass as a

								parameter.  Examples:


								    undef $foo;

								    undef $bar{'blurfl'};      # Compare to: delete $bar{'blurfl'};

								    undef @ary;

								    undef %hash;

								    undef &mysub;

								    undef *xyz;       # destroys $xyz, @xyz, %xyz, &xyz, etc.

								    return (wantarray ? (undef, $errmsg) : undef) if $they_blew_it;

								    select undef, undef, undef, 0.25;

								    ($a, $b, undef, $c) = &foo;       # Ignore third value returned


								Note that this is a unary operator, not a list operator.


								=item unlink LIST


								=item unlink


								Deletes a list of files.  Returns the number of files successfully

								deleted.


								    $cnt = unlink 'a', 'b', 'c';

								    unlink @goners;

								    unlink <*.bak>;


								Note: C<unlink> will not delete directories unless you are superuser and

								the B<-U> flag is supplied to Perl.  Even if these conditions are

								met, be warned that unlinking a directory can inflict damage on your

								filesystem.  Use C<rmdir> instead.


								If LIST is omitted, uses C<$_>.


								=item unpack TEMPLATE,EXPR


								C<unpack> does the reverse of C<pack>: it takes a string

								and expands it out into a list of values.

								(In scalar context, it returns merely the first value produced.)


								The string is broken into chunks described by the TEMPLATE.  Each chunk

								is converted separately to a value.  Typically, either the string is a result

								of C<pack>, or the bytes of the string represent a C structure of some

								kind.


								The TEMPLATE has the same format as in the C<pack> function.

								Here's a subroutine that does substring:


								    sub substr {

									my($what,$where,$howmuch) = @_;

									unpack("x$where a$howmuch", $what);

								    }


								and then there's


								    sub ordinal { unpack("c",$_[0]); } # same as ord()


								In addition to fields allowed in pack(), you may prefix a field with

								a %<number> to indicate that

								you want a <number>-bit checksum of the items instead of the items

								themselves.  Default is a 16-bit checksum.  Checksum is calculated by

								summing numeric values of expanded values (for string fields the sum of

								C<ord($char)> is taken, for bit fields the sum of zeroes and ones).


								For example, the following

								computes the same number as the System V sum program:


								    $checksum = do {

									local $/;  # slurp!

									unpack("%32C*",<>) % 65535;

								    };


								The following efficiently counts the number of set bits in a bit vector:


								    $setbits = unpack("%32b*", $selectmask);


								The C<p> and C<P> formats should be used with care.  Since Perl

								has no way of checking whether the value passed to C<unpack()>

								corresponds to a valid memory location, passing a pointer value that's

								not known to be valid is likely to have disastrous consequences.


								If the repeat count of a field is larger than what the remainder of

								the input string allows, repeat count is decreased.  If the input string

								is longer than one described by the TEMPLATE, the rest is ignored.


								See L</pack> for more examples and notes.


								=item untie VARIABLE


								Breaks the binding between a variable and a package.  (See C<tie>.)


								=item unshift ARRAY,LIST


								Does the opposite of a C<shift>.  Or the opposite of a C<push>,

								depending on how you look at it.  Prepends list to the front of the

								array, and returns the new number of elements in the array.


								    unshift(ARGV, '-e') unless $ARGV[0] =~ /^-/;


								Note the LIST is prepended whole, not one element at a time, so the

								prepended elements stay in the same order.  Use C<reverse> to do the

								reverse.


								=item use Module VERSION LIST


								=item use Module VERSION


								=item use Module LIST


								=item use Module


								=item use VERSION


								Imports some semantics into the current package from the named module,

								generally by aliasing certain subroutine or variable names into your

								package.  It is exactly equivalent to


								    BEGIN { require Module; import Module LIST; }


								except that Module I<must> be a bareword.


								VERSION, which can be specified as a literal of the form v5.6.1, demands

								that the current version of Perl (C<$^V> or $PERL_VERSION) be at least

								as recent as that version.  (For compatibility with older versions of Perl,

								a numeric literal will also be interpreted as VERSION.)  If the version

								of the running Perl interpreter is less than VERSION, then an error

								message is printed and Perl exits immediately without attempting to

								parse the rest of the file.  Compare with L</require>, which can do a

								similar check at run time.


								    use v5.6.1;		# compile time version check

								    use 5.6.1;		# ditto

								    use 5.005_03;	# float version allowed for compatibility


								This is often useful if you need to check the current Perl version before

								C<use>ing library modules that have changed in incompatible ways from

								older versions of Perl.  (We try not to do this more than we have to.)


								The C<BEGIN> forces the C<require> and C<import> to happen at compile time.  The

								C<require> makes sure the module is loaded into memory if it hasn't been

								yet.  The C<import> is not a builtin--it's just an ordinary static method

								call into the C<Module> package to tell the module to import the list of

								features back into the current package.  The module can implement its

								C<import> method any way it likes, though most modules just choose to

								derive their C<import> method via inheritance from the C<Exporter> class that

								is defined in the C<Exporter> module.  See L<Exporter>.  If no C<import>

								method can be found then the call is skipped.


								If you do not want to call the package's C<import> method (for instance,

								to stop your namespace from being altered), explicitly supply the empty list:


								    use Module ();


								That is exactly equivalent to


								    BEGIN { require Module }


								If the VERSION argument is present between Module and LIST, then the

								C<use> will call the VERSION method in class Module with the given

								version as an argument.  The default VERSION method, inherited from

								the UNIVERSAL class, croaks if the given version is larger than the

								value of the variable C<$Module::VERSION>.


								Again, there is a distinction between omitting LIST (C<import> called

								with no arguments) and an explicit empty LIST C<()> (C<import> not

								called).  Note that there is no comma after VERSION!


								Because this is a wide-open interface, pragmas (compiler directives)

								are also implemented this way.  Currently implemented pragmas are:


								    use constant;

								    use diagnostics;

								    use integer;

								    use sigtrap  qw(SEGV BUS);

								    use strict   qw(subs vars refs);

								    use subs     qw(afunc blurfl);

								    use warnings qw(all);


								Some of these pseudo-modules import semantics into the current

								block scope (like C<strict> or C<integer>, unlike ordinary modules,

								which import symbols into the current package (which are effective

								through the end of the file).


								There's a corresponding C<no> command that unimports meanings imported

								by C<use>, i.e., it calls C<unimport Module LIST> instead of C<import>.


								    no integer;

								    no strict 'refs';

								    no warnings;


								If no C<unimport> method can be found the call fails with a fatal error.


								See L<perlmodlib> for a list of standard modules and pragmas.  See L<perlrun>

								for the C<-M> and C<-m> command-line options to perl that give C<use>

								functionality from the command-line.


								=item utime LIST


								Changes the access and modification times on each file of a list of

								files.  The first two elements of the list must be the NUMERICAL access

								and modification times, in that order.  Returns the number of files

								successfully changed.  The inode change time of each file is set

								to the current time.  This code has the same effect as the C<touch>

								command if the files already exist:


								    #!/usr/bin/perl

								    $now = time;

								    utime $now, $now, @ARGV;


								=item values HASH


								Returns a list consisting of all the values of the named hash.  (In a

								scalar context, returns the number of values.)  The values are

								returned in an apparently random order.  The actual random order is

								subject to change in future versions of perl, but it is guaranteed to

								be the same order as either the C<keys> or C<each> function would

								produce on the same (unmodified) hash.


								Note that the values are not copied, which means modifying them will

								modify the contents of the hash:


								    for (values %hash) 	    { s/foo/bar/g }   # modifies %hash values

								    for (@hash{keys %hash}) { s/foo/bar/g }   # same


								As a side effect, calling values() resets the HASH's internal iterator.

								See also C<keys>, C<each>, and C<sort>.


								=item vec EXPR,OFFSET,BITS


								Treats the string in EXPR as a bit vector made up of elements of

								width BITS, and returns the value of the element specified by OFFSET

								as an unsigned integer.  BITS therefore specifies the number of bits

								that are reserved for each element in the bit vector.  This must

								be a power of two from 1 to 32 (or 64, if your platform supports

								that).


								If BITS is 8, "elements" coincide with bytes of the input string.


								If BITS is 16 or more, bytes of the input string are grouped into chunks

								of size BITS/8, and each group is converted to a number as with

								pack()/unpack() with big-endian formats C<n>/C<N> (and analogously

								for BITS==64).  See L<"pack"> for details.


								If bits is 4 or less, the string is broken into bytes, then the bits

								of each byte are broken into 8/BITS groups.  Bits of a byte are

								numbered in a little-endian-ish way, as in C<0x01>, C<0x02>,

								C<0x04>, C<0x08>, C<0x10>, C<0x20>, C<0x40>, C<0x80>.  For example,

								breaking the single input byte C<chr(0x36)> into two groups gives a list

								C<(0x6, 0x3)>; breaking it into 4 groups gives C<(0x2, 0x1, 0x3, 0x0)>.


								C<vec> may also be assigned to, in which case parentheses are needed

								to give the expression the correct precedence as in


								    vec($image, $max_x * $x + $y, 8) = 3;


								If the selected element is outside the string, the value 0 is returned.

								If an element off the end of the string is written to, Perl will first

								extend the string with sufficiently many zero bytes.   It is an error

								to try to write off the beginning of the string (i.e. negative OFFSET).


								The string should not contain any character with the value > 255 (which

								can only happen if you're using UTF8 encoding).  If it does, it will be

								treated as something which is not UTF8 encoded.  When the C<vec> was

								assigned to, other parts of your program will also no longer consider the

								string to be UTF8 encoded.  In other words, if you do have such characters

								in your string, vec() will operate on the actual byte string, and not the

								conceptual character string.


								Strings created with C<vec> can also be manipulated with the logical

								operators C<|>, C<&>, C<^>, and C<~>.  These operators will assume a bit

								vector operation is desired when both operands are strings.

								See L<perlop/"Bitwise String Operators">.


								The following code will build up an ASCII string saying C<'PerlPerlPerl'>.

								The comments show the string after each step.  Note that this code works

								in the same way on big-endian or little-endian machines.


								    my $foo = '';

								    vec($foo,  0, 32) = 0x5065726C;	# 'Perl'


								    # $foo eq "Perl" eq "\x50\x65\x72\x6C", 32 bits

								    print vec($foo, 0, 8);		# prints 80 == 0x50 == ord('P')


								    vec($foo,  2, 16) = 0x5065;		# 'PerlPe'

								    vec($foo,  3, 16) = 0x726C;		# 'PerlPerl'

								    vec($foo,  8,  8) = 0x50;		# 'PerlPerlP'

								    vec($foo,  9,  8) = 0x65;		# 'PerlPerlPe'

								    vec($foo, 20,  4) = 2;		# 'PerlPerlPe'   . "\x02"

								    vec($foo, 21,  4) = 7;		# 'PerlPerlPer'

								                                        # 'r' is "\x72"

								    vec($foo, 45,  2) = 3;		# 'PerlPerlPer'  . "\x0c"

								    vec($foo, 93,  1) = 1;		# 'PerlPerlPer'  . "\x2c"

								    vec($foo, 94,  1) = 1;		# 'PerlPerlPerl'

								                                        # 'l' is "\x6c"


								To transform a bit vector into a string or list of 0's and 1's, use these:


								    $bits = unpack("b*", $vector);

								    @bits = split(//, unpack("b*", $vector));


								If you know the exact length in bits, it can be used in place of the C<*>.


								Here is an example to illustrate how the bits actually fall in place:


								    #!/usr/bin/perl -wl


								    print <<'EOT';

								                                      0         1         2         3

								                       unpack("V",$_) 01234567890123456789012345678901

								    ------------------------------------------------------------------

								    EOT


								    for $w (0..3) {

								        $width = 2**$w;

								        for ($shift=0; $shift < $width; ++$shift) {

								            for ($off=0; $off < 32/$width; ++$off) {

								                $str = pack("B*", "0"x32);

								                $bits = (1<<$shift);

								                vec($str, $off, $width) = $bits;

								                $res = unpack("b*",$str);

								                $val = unpack("V", $str);

								                write;

								            }

								        }

								    }


								    format STDOUT =

								    vec($_,@#,@#) = @<< == @######### @>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

								    $off, $width, $bits, $val, $res

								    .

								    __END__


								Regardless of the machine architecture on which it is run, the above

								example should print the following table:


								                                      0         1         2         3

								                       unpack("V",$_) 01234567890123456789012345678901

								    ------------------------------------------------------------------

								    vec($_, 0, 1) = 1   ==          1 10000000000000000000000000000000

								    vec($_, 1, 1) = 1   ==          2 01000000000000000000000000000000

								    vec($_, 2, 1) = 1   ==          4 00100000000000000000000000000000

								    vec($_, 3, 1) = 1   ==          8 00010000000000000000000000000000

								    vec($_, 4, 1) = 1   ==         16 00001000000000000000000000000000

								    vec($_, 5, 1) = 1   ==         32 00000100000000000000000000000000

								    vec($_, 6, 1) = 1   ==         64 00000010000000000000000000000000

								    vec($_, 7, 1) = 1   ==        128 00000001000000000000000000000000

								    vec($_, 8, 1) = 1   ==        256 00000000100000000000000000000000

								    vec($_, 9, 1) = 1   ==        512 00000000010000000000000000000000

								    vec($_,10, 1) = 1   ==       1024 00000000001000000000000000000000

								    vec($_,11, 1) = 1   ==       2048 00000000000100000000000000000000

								    vec($_,12, 1) = 1   ==       4096 00000000000010000000000000000000

								    vec($_,13, 1) = 1   ==       8192 00000000000001000000000000000000

								    vec($_,14, 1) = 1   ==      16384 00000000000000100000000000000000

								    vec($_,15, 1) = 1   ==      32768 00000000000000010000000000000000

								    vec($_,16, 1) = 1   ==      65536 00000000000000001000000000000000

								    vec($_,17, 1) = 1   ==     131072 00000000000000000100000000000000

								    vec($_,18, 1) = 1   ==     262144 00000000000000000010000000000000

								    vec($_,19, 1) = 1   ==     524288 00000000000000000001000000000000

								    vec($_,20, 1) = 1   ==    1048576 00000000000000000000100000000000

								    vec($_,21, 1) = 1   ==    2097152 00000000000000000000010000000000

								    vec($_,22, 1) = 1   ==    4194304 00000000000000000000001000000000

								    vec($_,23, 1) = 1   ==    8388608 00000000000000000000000100000000

								    vec($_,24, 1) = 1   ==   16777216 00000000000000000000000010000000

								    vec($_,25, 1) = 1   ==   33554432 00000000000000000000000001000000

								    vec($_,26, 1) = 1   ==   67108864 00000000000000000000000000100000

								    vec($_,27, 1) = 1   ==  134217728 00000000000000000000000000010000

								    vec($_,28, 1) = 1   ==  268435456 00000000000000000000000000001000

								    vec($_,29, 1) = 1   ==  536870912 00000000000000000000000000000100

								    vec($_,30, 1) = 1   == 1073741824 00000000000000000000000000000010

								    vec($_,31, 1) = 1   == 2147483648 00000000000000000000000000000001

								    vec($_, 0, 2) = 1   ==          1 10000000000000000000000000000000

								    vec($_, 1, 2) = 1   ==          4 00100000000000000000000000000000

								    vec($_, 2, 2) = 1   ==         16 00001000000000000000000000000000

								    vec($_, 3, 2) = 1   ==         64 00000010000000000000000000000000

								    vec($_, 4, 2) = 1   ==        256 00000000100000000000000000000000

								    vec($_, 5, 2) = 1   ==       1024 00000000001000000000000000000000

								    vec($_, 6, 2) = 1   ==       4096 00000000000010000000000000000000

								    vec($_, 7, 2) = 1   ==      16384 00000000000000100000000000000000

								    vec($_, 8, 2) = 1   ==      65536 00000000000000001000000000000000

								    vec($_, 9, 2) = 1   ==     262144 00000000000000000010000000000000

								    vec($_,10, 2) = 1   ==    1048576 00000000000000000000100000000000

								    vec($_,11, 2) = 1   ==    4194304 00000000000000000000001000000000

								    vec($_,12, 2) = 1   ==   16777216 00000000000000000000000010000000

								    vec($_,13, 2) = 1   ==   67108864 00000000000000000000000000100000

								    vec($_,14, 2) = 1   ==  268435456 00000000000000000000000000001000

								    vec($_,15, 2) = 1   == 1073741824 00000000000000000000000000000010

								    vec($_, 0, 2) = 2   ==          2 01000000000000000000000000000000

								    vec($_, 1, 2) = 2   ==          8 00010000000000000000000000000000

								    vec($_, 2, 2) = 2   ==         32 00000100000000000000000000000000

								    vec($_, 3, 2) = 2   ==        128 00000001000000000000000000000000

								    vec($_, 4, 2) = 2   ==        512 00000000010000000000000000000000

								    vec($_, 5, 2) = 2   ==       2048 00000000000100000000000000000000

								    vec($_, 6, 2) = 2   ==       8192 00000000000001000000000000000000

								    vec($_, 7, 2) = 2   ==      32768 00000000000000010000000000000000

								    vec($_, 8, 2) = 2   ==     131072 00000000000000000100000000000000

								    vec($_, 9, 2) = 2   ==     524288 00000000000000000001000000000000

								    vec($_,10, 2) = 2   ==    2097152 00000000000000000000010000000000

								    vec($_,11, 2) = 2   ==    8388608 00000000000000000000000100000000

								    vec($_,12, 2) = 2   ==   33554432 00000000000000000000000001000000

								    vec($_,13, 2) = 2   ==  134217728 00000000000000000000000000010000

								    vec($_,14, 2) = 2   ==  536870912 00000000000000000000000000000100

								    vec($_,15, 2) = 2   == 2147483648 00000000000000000000000000000001

								    vec($_, 0, 4) = 1   ==          1 10000000000000000000000000000000

								    vec($_, 1, 4) = 1   ==         16 00001000000000000000000000000000

								    vec($_, 2, 4) = 1   ==        256 00000000100000000000000000000000

								    vec($_, 3, 4) = 1   ==       4096 00000000000010000000000000000000

								    vec($_, 4, 4) = 1   ==      65536 00000000000000001000000000000000

								    vec($_, 5, 4) = 1   ==    1048576 00000000000000000000100000000000

								    vec($_, 6, 4) = 1   ==   16777216 00000000000000000000000010000000

								    vec($_, 7, 4) = 1   ==  268435456 00000000000000000000000000001000

								    vec($_, 0, 4) = 2   ==          2 01000000000000000000000000000000

								    vec($_, 1, 4) = 2   ==         32 00000100000000000000000000000000

								    vec($_, 2, 4) = 2   ==        512 00000000010000000000000000000000

								    vec($_, 3, 4) = 2   ==       8192 00000000000001000000000000000000

								    vec($_, 4, 4) = 2   ==     131072 00000000000000000100000000000000

								    vec($_, 5, 4) = 2   ==    2097152 00000000000000000000010000000000

								    vec($_, 6, 4) = 2   ==   33554432 00000000000000000000000001000000

								    vec($_, 7, 4) = 2   ==  536870912 00000000000000000000000000000100

								    vec($_, 0, 4) = 4   ==          4 00100000000000000000000000000000

								    vec($_, 1, 4) = 4   ==         64 00000010000000000000000000000000

								    vec($_, 2, 4) = 4   ==       1024 00000000001000000000000000000000

								    vec($_, 3, 4) = 4   ==      16384 00000000000000100000000000000000

								    vec($_, 4, 4) = 4   ==     262144 00000000000000000010000000000000

								    vec($_, 5, 4) = 4   ==    4194304 00000000000000000000001000000000

								    vec($_, 6, 4) = 4   ==   67108864 00000000000000000000000000100000

								    vec($_, 7, 4) = 4   == 1073741824 00000000000000000000000000000010

								    vec($_, 0, 4) = 8   ==          8 00010000000000000000000000000000

								    vec($_, 1, 4) = 8   ==        128 00000001000000000000000000000000

								    vec($_, 2, 4) = 8   ==       2048 00000000000100000000000000000000

								    vec($_, 3, 4) = 8   ==      32768 00000000000000010000000000000000

								    vec($_, 4, 4) = 8   ==     524288 00000000000000000001000000000000

								    vec($_, 5, 4) = 8   ==    8388608 00000000000000000000000100000000

								    vec($_, 6, 4) = 8   ==  134217728 00000000000000000000000000010000

								    vec($_, 7, 4) = 8   == 2147483648 00000000000000000000000000000001

								    vec($_, 0, 8) = 1   ==          1 10000000000000000000000000000000

								    vec($_, 1, 8) = 1   ==        256 00000000100000000000000000000000

								    vec($_, 2, 8) = 1   ==      65536 00000000000000001000000000000000

								    vec($_, 3, 8) = 1   ==   16777216 00000000000000000000000010000000

								    vec($_, 0, 8) = 2   ==          2 01000000000000000000000000000000

								    vec($_, 1, 8) = 2   ==        512 00000000010000000000000000000000

								    vec($_, 2, 8) = 2   ==     131072 00000000000000000100000000000000

								    vec($_, 3, 8) = 2   ==   33554432 00000000000000000000000001000000

								    vec($_, 0, 8) = 4   ==          4 00100000000000000000000000000000

								    vec($_, 1, 8) = 4   ==       1024 00000000001000000000000000000000

								    vec($_, 2, 8) = 4   ==     262144 00000000000000000010000000000000

								    vec($_, 3, 8) = 4   ==   67108864 00000000000000000000000000100000

								    vec($_, 0, 8) = 8   ==          8 00010000000000000000000000000000

								    vec($_, 1, 8) = 8   ==       2048 00000000000100000000000000000000

								    vec($_, 2, 8) = 8   ==     524288 00000000000000000001000000000000

								    vec($_, 3, 8) = 8   ==  134217728 00000000000000000000000000010000

								    vec($_, 0, 8) = 16  ==         16 00001000000000000000000000000000

								    vec($_, 1, 8) = 16  ==       4096 00000000000010000000000000000000

								    vec($_, 2, 8) = 16  ==    1048576 00000000000000000000100000000000

								    vec($_, 3, 8) = 16  ==  268435456 00000000000000000000000000001000

								    vec($_, 0, 8) = 32  ==         32 00000100000000000000000000000000

								    vec($_, 1, 8) = 32  ==       8192 00000000000001000000000000000000

								    vec($_, 2, 8) = 32  ==    2097152 00000000000000000000010000000000

								    vec($_, 3, 8) = 32  ==  536870912 00000000000000000000000000000100

								    vec($_, 0, 8) = 64  ==         64 00000010000000000000000000000000

								    vec($_, 1, 8) = 64  ==      16384 00000000000000100000000000000000

								    vec($_, 2, 8) = 64  ==    4194304 00000000000000000000001000000000

								    vec($_, 3, 8) = 64  == 1073741824 00000000000000000000000000000010

								    vec($_, 0, 8) = 128 ==        128 00000001000000000000000000000000

								    vec($_, 1, 8) = 128 ==      32768 00000000000000010000000000000000

								    vec($_, 2, 8) = 128 ==    8388608 00000000000000000000000100000000

								    vec($_, 3, 8) = 128 == 2147483648 00000000000000000000000000000001


								=item wait


								Behaves like the wait(2) system call on your system: it waits for a child

								process to terminate and returns the pid of the deceased process, or

								C<-1> if there are no child processes.  The status is returned in C<$?>.

								Note that a return value of C<-1> could mean that child processes are

								being automatically reaped, as described in L<perlipc>.


								=item waitpid PID,FLAGS


								Waits for a particular child process to terminate and returns the pid of

								the deceased process, or C<-1> if there is no such child process.  On some

								systems, a value of 0 indicates that there are processes still running.

								The status is returned in C<$?>.  If you say


								    use POSIX ":sys_wait_h";

								    #...

								    do {

									$kid = waitpid(-1,&WNOHANG);

								    } until $kid == -1;


								then you can do a non-blocking wait for all pending zombie processes.

								Non-blocking wait is available on machines supporting either the

								waitpid(2) or wait4(2) system calls.  However, waiting for a particular

								pid with FLAGS of C<0> is implemented everywhere.  (Perl emulates the

								system call by remembering the status values of processes that have

								exited but have not been harvested by the Perl script yet.)


								Note that on some systems, a return value of C<-1> could mean that child

								processes are being automatically reaped.  See L<perlipc> for details,

								and for other examples.


								=item wantarray


								Returns true if the context of the currently executing subroutine is

								looking for a list value.  Returns false if the context is looking

								for a scalar.  Returns the undefined value if the context is looking

								for no value (void context).


								    return unless defined wantarray;	# don't bother doing more

								    my @a = complex_calculation();

								    return wantarray ? @a : "@a";


								This function should have been named wantlist() instead.


								=item warn LIST


								Produces a message on STDERR just like C<die>, but doesn't exit or throw

								an exception.


								If LIST is empty and C<$@> already contains a value (typically from a

								previous eval) that value is used after appending C<"\t...caught">

								to C<$@>.  This is useful for staying almost, but not entirely similar to

								C<die>.


								If C<$@> is empty then the string C<"Warning: Something's wrong"> is used.


								No message is printed if there is a C<$SIG{__WARN__}> handler

								installed.  It is the handler's responsibility to deal with the message

								as it sees fit (like, for instance, converting it into a C<die>).  Most

								handlers must therefore make arrangements to actually display the

								warnings that they are not prepared to deal with, by calling C<warn>

								again in the handler.  Note that this is quite safe and will not

								produce an endless loop, since C<__WARN__> hooks are not called from

								inside one.


								You will find this behavior is slightly different from that of

								C<$SIG{__DIE__}> handlers (which don't suppress the error text, but can

								instead call C<die> again to change it).


								Using a C<__WARN__> handler provides a powerful way to silence all

								warnings (even the so-called mandatory ones).  An example:


								    # wipe out *all* compile-time warnings

								    BEGIN { $SIG{'__WARN__'} = sub { warn $_[0] if $DOWARN } }

								    my $foo = 10;

								    my $foo = 20;          # no warning about duplicate my $foo,

								                           # but hey, you asked for it!

								    # no compile-time or run-time warnings before here

								    $DOWARN = 1;


								    # run-time warnings enabled after here

								    warn "\$foo is alive and $foo!";     # does show up


								See L<perlvar> for details on setting C<%SIG> entries, and for more

								examples.  See the Carp module for other kinds of warnings using its

								carp() and cluck() functions.


								=item write FILEHANDLE


								=item write EXPR


								=item write


								Writes a formatted record (possibly multi-line) to the specified FILEHANDLE,

								using the format associated with that file.  By default the format for

								a file is the one having the same name as the filehandle, but the

								format for the current output channel (see the C<select> function) may be set

								explicitly by assigning the name of the format to the C<$~> variable.


								Top of form processing is handled automatically:  if there is

								insufficient room on the current page for the formatted record, the

								page is advanced by writing a form feed, a special top-of-page format

								is used to format the new page header, and then the record is written.

								By default the top-of-page format is the name of the filehandle with

								"_TOP" appended, but it may be dynamically set to the format of your

								choice by assigning the name to the C<$^> variable while the filehandle is

								selected.  The number of lines remaining on the current page is in

								variable C<$->, which can be set to C<0> to force a new page.


								If FILEHANDLE is unspecified, output goes to the current default output

								channel, which starts out as STDOUT but may be changed by the

								C<select> operator.  If the FILEHANDLE is an EXPR, then the expression

								is evaluated and the resulting string is used to look up the name of

								the FILEHANDLE at run time.  For more on formats, see L<perlform>.


								Note that write is I<not> the opposite of C<read>.  Unfortunately.


								=item y///


								The transliteration operator.  Same as C<tr///>.  See L<perlop>.


								=back