First; how it should work: Let's imagine your module is Food::Product. Food::Product creates instances (objects). Let's try to instance a food product.. (code untested)

use Food::Product;
my $p = new Food::Product('Tomato')
   or die("Could not instance Food::Product: ($Food::Product::errstr)"
+);

$p->isle(14);
$p->stock(450);
$p->sell(450) or die($p->errstr);
$p->sell(40) or die($p->errstr);
[download]

Example of what is inside Food::Product

package Food::Product;
use strict;
use LEOCHARRE::Class2; # you do this your way
use vars qw/$errstr/;
__PACKAGE__->make_accessor_setget(qw/isle stock errst/);

sub new {
   my($class,$arg)=@_;
   $arg 
      or $errstr = "Missing valid arg"
      and return;
   return { name => $arg }, $class;
}

sub sell {
   my($self,$count)=@_;
   $count 
      or $self->errstr('missing how much to sell ammount')
      and return;

   my $now = $self->stock
      or $self->errstr('no stock left to sell from')
      and return;

   my $left_over = ( $now - $count ) ... some other rationalle
   $self->stock($left_over);
}
[download]

So in above examples.

• $Food::Product::errstr is a class symbol holding error string (potentially). These are class wide errors- maybe on compile, some config file should be present in the system- etc.
• Food::Product::errstr() is a method for the object- a regular perl setget method. This hold errors in regards to this one object. If you give it a bad name, a faulty parameter.. etc.

Check out DBI, has some similarities.
I used to fumble with this, wondering if maybe $error was better a label.. but errstr is pretty freaking common.

So, to answer more directly. In c, it's common to return if something is up- in perl, we return when it's all good. So, store any messages in the class or object as a separate value. Do NOT assume the coder wants to access further information if something fails. Just make it possible to get more information. Whatever you do- don't return only if there's an error etc- that would be poor form in perl.

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