Perl::Critic::Policy::RegularExpressions::ProhibitUselessTopic - Don't use $_ to match against regexes.

       This Policy is part of the Perl::Critic distribution.

       Andy Lester <andy@petdance.com>

       This Policy is not configurable except for the standard options.

       Copyright (c) 2013-2023 Andy Lester <andy@petdance.com>

       This library is free software; you can redistribute it and/or modify it under the terms of the Artistic
       License 2.0.

perl v5.40.0                                       2024-10-28             Perl::Critic::P...bitUselessTopic(3pm)

       It is not necessary to specify the topic variable $_ when matching against a regular expression.

       Match or substitution operations are performed against variables, such as:

           $x =~ /foo/;
           $x =~ s/foo/bar/;
           $x =~ tr/a-mn-z/n-za-m/;

       If a variable is not specified, the match is against $_.

           # These are identical.
           /foo/;
           $_ =~ /foo/;

           # These are identical.
           s/foo/bar/;
           $_ =~ s/foo/bar/;

           # These are identical.
           tr/a-mn-z/n-za-m/;
           $_ =~ tr/a-mn-z/n-za-m/;

       This applies to negative matching as well.

           # These are identical
           if ( $_ !~ /DEBUG/ ) { ...
           if ( !/DEBUG ) { ...

       Including the "$_ =~" or "$_ !~" is unnecessary, adds complexity, and is not idiomatic Perl.

       Perl::Critic::Policy::RegularExpressions::ProhibitUselessTopic - Don't use $_ to match against regexes.