#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