Yeah, you're right, looks like I got them the wrong way around . As for talking to the end-user from a module, I think using carp for that is an elegant solution, especially when it's something that can be toggled on and off using a flag. For example:

package Foo;

use strict;
use warnings;

sub new
  {
  my($class, $debug) = @_;
  my $self = {};
  bless($self, $class);
  if($debug)
    { $self->{'Debug'} = 1; }
  return $self;
  }

sub bar
  {
  my($self, $hashref, @arguments) = @_;
  unless(ref($hashref) eq 'HASH')
    {
    if($debug)
      { carp "ERROR: first argument to \'bar\' must be a hashref"; }
    return;
    }
  #insert code here
  return $result;
  }
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I find carp most useful for these cases. Personally I feel a module should never die on its own, that's my decision...