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root |
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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 |
