You have your inheritance the wrong way round. Cats and dogs are types of animal, so the Cat and Dog classes need to inherit from Animal - not the other way round.

package Animal;

sub new {
  my $class = shift;
  my $self  = {};
  bless ($self, $class);
  return $self;
}

1;

-------------------------------------------------------------------

package Cat;
use strict;

use Animal;
our @ISA = qw(Animal);

sub speak {
  print "meow...\n";
}

1;

-------------------------------------------------------------------

package Dog;
use strict;

use Animal;
our @ISA = qw(Animal);

sub speak {
  print "woof...\n";
}

1;

---------------------------------------------------------

#!/usr/bin/perl

use strict;
use warnings;

use Dog;
use Cat;

my $dog = Dog->new();
my $cat = Cat->new();

$dog->speak;
$cat->speak;

[download]

I've also removed the "ref($proto) || $proto" cargo-culting from your code. If you want people to be able to call your constructor as an object method as well as a class method then you should probably have another (object method) constructor called "clone" or "copy". It's generally considered bad practice to have one constructor that is used as both.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg

In reply to Re: OO & multiple inheritance. by davorg
in thread OO & multiple inheritance. by yoda54

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