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ELLIOTJS / Perl-Critic-1.107_001 / lib / Perl / Critic / Policy / Variables / ProhibitMatchVars.pm 

            

              
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##############################################################################
#      $URL: http://perlcritic.tigris.org/svn/perlcritic/trunk/distributions/Perl-Critic/lib/Perl/Critic/Policy/Variables/ProhibitMatchVars.pm $
#     $Date: 2010-06-13 18:26:31 -0500 (Sun, 13 Jun 2010) $
#   $Author: clonezone $
# $Revision: 3824 $
##############################################################################
package Perl::Critic::Policy::Variables::ProhibitMatchVars;
use 5.006001;
use strict;
use warnings;
use Readonly;
use Perl::Critic::Utils qw{ :severities :data_conversion };
use base 'Perl::Critic::Policy';
our $VERSION = '1.107_001';
#-----------------------------------------------------------------------------
Readonly::Scalar my $DESC => q{Match variable used};
Readonly::Scalar my $EXPL => [ 82 ];
Readonly::Array my @FORBIDDEN => qw( $` $& $' $MATCH $PREMATCH $POSTMATCH );
Readonly::Hash my %FORBIDDEN => hashify( @FORBIDDEN );
#-----------------------------------------------------------------------------
sub supported_parameters { return ()                         }
sub default_severity     { return $SEVERITY_HIGH             }
sub default_themes       { return qw( core performance pbp ) }
sub applies_to           { return qw( PPI::Token::Symbol
                                      PPI::Statement::Include ) }
#-----------------------------------------------------------------------------
sub violates {
    my ( $self, $elem, undef ) = @_;
    if (_is_use_english($elem) || _is_forbidden_var($elem)) {
        return $self->violation( $DESC, $EXPL, $elem );
    }
    return;  #ok!
}
#-----------------------------------------------------------------------------
sub _is_use_english {
    my $elem = shift;
    $elem->isa('PPI::Statement::Include') || return;
    $elem->type() eq 'use' || return;
    $elem->module() eq 'English' || return;
    # Bare, lacking -no_match_vars.  Now handled by
    # Modules::RequireNoMatchVarsWithUseEnglish.
    return 0 if ($elem =~ m/\A use \s+ English \s* ;\z/xms);
    return 1 if ($elem =~ m/\$(?:PRE|POST|)MATCH/xms);
    return;  # either "-no_match_vars" or a specific list
}
sub _is_forbidden_var {
    my $elem = shift;
    $elem->isa('PPI::Token::Symbol') || return;
    return exists $FORBIDDEN{$elem};
}
1;
__END__
#-----------------------------------------------------------------------------
=pod
=head1 NAME
Perl::Critic::Policy::Variables::ProhibitMatchVars - Avoid C<$`>, C<$&>, C<$'> and their English equivalents.
=head1 AFFILIATION
This Policy is part of the core L<Perl::Critic|Perl::Critic>
distribution.
=head1 DESCRIPTION
Using the "match variables" C<$`>, C<$&>, and/or C<$'> can
significantly degrade the performance of a program.  This policy
forbids using them or their English equivalents.  See B<perldoc
English> or PBP page 82 for more information.
It used to forbid plain C<use English;> because it ends up causing the
performance side-effects of the match variables.  However, the message
emitted for that situation was not at all clear and there is now
L<Perl::Critic::Policy::Modules::RequireNoMatchVarsWithUseEnglish|Perl::Critic::Policy::Modules::RequireNoMatchVarsWithUseEnglish>,
which addresses this situation directly.
=head1 CONFIGURATION
This Policy is not configurable except for the standard options.
=head1 AUTHOR
Chris Dolan <cdolan@cpan.org>
=head1 COPYRIGHT
Copyright (c) 2006-2010 Chris Dolan.
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.  The full text of this license
can be found in the LICENSE file included with this module.
=cut
# Local Variables:
#   mode: cperl
#   cperl-indent-level: 4
#   fill-column: 78
#   indent-tabs-mode: nil
#   c-indentation-style: bsd
# End:
# ex: set ts=8 sts=4 sw=4 tw=78 ft=perl expandtab shiftround :