package Your::Forager;
use base 'Badger::Base';

our $DEBUG    = 0 unless defined $DEBUG;
our $MESSAGES = {
    foraging => 'Foraging in the %s for %s',

sub forage {
    my ($self, $where, $what) = @_;
    $self->debug_msg( foraging => $where, $what ) if $DEBUG;
    # ... do some foraging...
Thus Spake Andy:

It should be obvious that you don't want your debugging on all the time. A common trick is to use a package variable like $DEBUG and put an if $DEBUG guard expression at the end of each debugging line. Also note how we only default $DEBUG to 0 if it's not already defined. This is so that you can set $DEBUG before loading the module to over-ride the default value of 0.

The downside to using a package variable is that Perl has to test it for each and every debugging line. Sure, it's not much, but it adds up, particularly in time-critical sections of code.