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136 lines
3.2 KiB
136 lines
3.2 KiB
package strict;
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$strict::VERSION = "1.03";
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my %bitmask = (
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refs => 0x00000002,
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subs => 0x00000200,
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vars => 0x00000400
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);
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sub bits {
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my $bits = 0;
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my @wrong;
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foreach my $s (@_) {
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push @wrong, $s unless exists $bitmask{$s};
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$bits |= $bitmask{$s} || 0;
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}
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if (@wrong) {
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require Carp;
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Carp::croak("Unknown 'strict' tag(s) '@wrong'");
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}
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$bits;
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}
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my $default_bits = bits(qw(refs subs vars));
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sub import {
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shift;
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$^H |= @_ ? bits(@_) : $default_bits;
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}
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sub unimport {
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shift;
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$^H &= ~ (@_ ? bits(@_) : $default_bits);
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}
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1;
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__END__
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=head1 NAME
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strict - Perl pragma to restrict unsafe constructs
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=head1 SYNOPSIS
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use strict;
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use strict "vars";
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use strict "refs";
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use strict "subs";
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use strict;
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no strict "vars";
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=head1 DESCRIPTION
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If no import list is supplied, all possible restrictions are assumed.
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(This is the safest mode to operate in, but is sometimes too strict for
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casual programming.) Currently, there are three possible things to be
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strict about: "subs", "vars", and "refs".
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=over 6
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=item C<strict refs>
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This generates a runtime error if you
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use symbolic references (see L<perlref>).
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use strict 'refs';
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$ref = \$foo;
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print $$ref; # ok
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$ref = "foo";
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print $$ref; # runtime error; normally ok
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$file = "STDOUT";
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print $file "Hi!"; # error; note: no comma after $file
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There is one exception to this rule:
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$bar = \&{'foo'};
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&$bar;
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is allowed so that C<goto &$AUTOLOAD> would not break under stricture.
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=item C<strict vars>
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This generates a compile-time error if you access a variable that wasn't
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declared via C<our> or C<use vars>,
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localized via C<my()>, or wasn't fully qualified. Because this is to avoid
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variable suicide problems and subtle dynamic scoping issues, a merely
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local() variable isn't good enough. See L<perlfunc/my> and
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L<perlfunc/local>.
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use strict 'vars';
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$X::foo = 1; # ok, fully qualified
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my $foo = 10; # ok, my() var
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local $foo = 9; # blows up
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package Cinna;
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our $bar; # Declares $bar in current package
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$bar = 'HgS'; # ok, global declared via pragma
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The local() generated a compile-time error because you just touched a global
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name without fully qualifying it.
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Because of their special use by sort(), the variables $a and $b are
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exempted from this check.
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=item C<strict subs>
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This disables the poetry optimization, generating a compile-time error if
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you try to use a bareword identifier that's not a subroutine, unless it
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is a simple identifier (no colons) and that it appears in curly braces or
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on the left hand side of the C<< => >> symbol.
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use strict 'subs';
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$SIG{PIPE} = Plumber; # blows up
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$SIG{PIPE} = "Plumber"; # just fine: quoted string is always ok
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$SIG{PIPE} = \&Plumber; # preferred form
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=back
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See L<perlmodlib/Pragmatic Modules>.
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=head1 HISTORY
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C<strict 'subs'>, with Perl 5.6.1, erroneously permitted to use an unquoted
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compound identifier (e.g. C<Foo::Bar>) as a hash key (before C<< => >> or
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inside curlies), but without forcing it always to a literal string.
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Starting with Perl 5.8.1 strict is strict about its restrictions:
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if unknown restrictions are used, the strict pragma will abort with
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Unknown 'strict' tag(s) '...'
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=cut
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