Perl::Critic::Policy::Variables::ProhibitReusedNames3pm

Affiliation

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

Overview

It's really hard on future maintenance programmers if you reuse a variable name in a lexical scope. The programmer is at risk of confusing which variable is which. And, worse, the programmer could accidentally remove the inner declaration, thus silently changing the meaning of the inner code to use the outer variable.

    my $x = 1;
    for my $i (0 .. 10) {
        my $x = $i+1;  # not OK, "$x" reused
    }

With "use warnings" in effect, Perl will warn you if you reuse a variable name at the same scope level but not within nested scopes. Like so:

    % perl -we 'my $x; my $x'
    "my" variable $x masks earlier declaration in same scope at -e line 1.

This policy takes that warning to a stricter level.

Caveats

    sub make_accessor {
        my ($self, $fieldname) = @_;
        return sub {
            my ($self) = @_;  # false positive, $self declared as reused
            return $self->{$fieldname};
        }
    }

    my $debug_mode = 0;
    sub set_debug {
        my $debug_mode = 1;  # accidental redeclaration
    }

Configuration

This policy has a single option, "allow", which is a list of names to never count as duplicates. It defaults to containing $self and $class. You add to this by adding something like this to your .perlcriticrc:

    [Variables::ProhibitReusedNames]
    allow = $self $class @blah