If this is in a module, i usually add a _debug key to my blessed hash and use a function with a name similar to dbg("Message"). All this function does is :

sub dbg {
  my ($self,$msg) = @_;
  return if (! $self->{_debug});
  print STDERR "[DEBUG] : $msg\n";
}
[download]

And, a simple accessor method like :

sub debug {
  my ($self,$val) = @_;
  $self->{_debug} = $val if (defined $val);
  $self->{_debug};
}
[download]

While this all may seem a bit elaborate, it is excedingly useful to have as a standard for every module. If the $main::DEBUG is the approach you prefer, there is always more than one way to do it, and changing dbg to the following would work :

sub dbg {
  my $msg = shift;
  print "[DEBUG] : $msg\n" if ($main::DEBUG);
}
[download]

---

OH, a sarcasm detector, that’s really useful