#!/usr/bin/perl
use warnings;
use strict;

use constant DEBUG => not undef;
use Data::Dumper;

BEGIN {
  my ($a, $b, $c) = (1, 2, 3);

  my $deb;
  if (DEBUG) {
    $deb = sub {
      print Data::Dumper->Dump([$a, $b, $c], [qw/a b c/]);
    };
  } else {
    $deb = sub {
      warn "Debugging not enabled!\n";
    }
  }

  sub debug { &$deb }
}