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package strict;
=head1 NAME
strict - Perl pragma to restrict unsafe constructs
=head1 SYNOPSIS
use strict;
use strict "vars";
use strict "refs";
use strict "subs";
use strict;
no strict "vars";
=head1 DESCRIPTION
If no import list is supplied, all possible restrictions are assumed.
(This is the safest mode to operate in, but is sometimes too strict for
casual programming.) Currently, there are three possible things to be
strict about: "subs", "vars", and "refs".
=over 6
=item C<strict refs>
This generates a runtime error if you
use symbolic references (see L<perlref>).
use strict 'refs';
$ref = \$foo;
print $$ref; # ok
$ref = "foo";
print $$ref; # runtime error; normally ok
=item C<strict vars>
This generates a compile-time error if you access a variable that wasn't
localized via C<my()> or wasn't fully qualified. Because this is to avoid
variable suicide problems and subtle dynamic scoping issues, a merely
local() variable isn't good enough. See L<perlfunc/my> and
L<perlfunc/local>.
use strict 'vars';
$X::foo = 1; # ok, fully qualified
my $foo = 10; # ok, my() var
local $foo = 9; # blows up
The local() generated a compile-time error because you just touched a global
name without fully qualifying it.
=item C<strict subs>
This disables the poetry optimization, generating a compile-time error if
you try to use a bareword identifier that's not a subroutine, unless it
appears in curly braces or on the left hand side of the "=E<gt>" symbol.
use strict 'subs';
$SIG{PIPE} = Plumber; # blows up
$SIG{PIPE} = "Plumber"; # just fine: bareword in curlies always ok
$SIG{PIPE} = \&Plumber; # preferred form
=back
See L<perlmod/Pragmatic Modules>.
=cut
sub bits {
my $bits = 0;
my $sememe;
foreach $sememe (@_) {
$bits |= 0x00000002, next if $sememe eq 'refs';
$bits |= 0x00000200, next if $sememe eq 'subs';
$bits |= 0x00000400, next if $sememe eq 'vars';
}
$bits;
}
sub import {
shift;
$^H |= bits(@_ ? @_ : qw(refs subs vars));
}
sub unimport {
shift;
$^H &= ~ bits(@_ ? @_ : qw(refs subs vars));
}
1;
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