Perl::Critic::Policy::RegularExpressions::ProhibitUselessTopic(3)

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

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

DESCRIPTION
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.

CONFIGURATION
This Policy is not configurable except for the standard options.

AUTHOR
Andy Lester <andy@petdance.com>

COPYRIGHT
Copyright (c) 2013 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.