Perl::Critic::Policy::Variables::RequireLocalizedPunctuationVars3pm

Affiliation

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

Overview

Punctuation variables (and their English.pm equivalents) are global variables. Messing with globals is dangerous in a complex program as it can lead to very subtle and hard to fix bugs. If you must change a magic variable in a non-trivial program, do it in a local scope.

For example, to slurp a filehandle into a scalar, it's common to set the record separator to undef instead of a newline. If you choose to do this (instead of using Path::Tiny!) then be sure to localize the global and change it for as short a time as possible.

    # BAD:
    $/ = undef;
    my $content = <$fh>;
    # BETTER:
    my $content;
    {
        local $/ = undef;
        $content = <$fh>;
    }
    # A popular idiom:
    my $content = do { local $/ = undef; <$fh> };

This policy also allows the use of "my". Perl prevents using "my" with "proper" punctuation variables, but allows $a, @ARGV, the names declared by English, etc. This is not a good coding practice, however it is not the concern of this specific policy to complain about that.

There are exemptions for $_ and @_, and the English equivalent $ARG.

Configuration

You can configure your own exemptions using the "allow" option:

    [Variables::RequireLocalizedPunctuationVars]
    allow = @ARGV $ARGV

These are added to the default exemptions.

Credits

Initial development of this policy was supported by a grant from the Perl Foundation.