Thanks for the suggestion. I'll test these modules, a quickly look in the code shows that they use a different approach to declare abstract methods (using import) but the idea is basically the same.

In the other hand Class::Virtually::Abstract will not work with code generator modules and it uses eval, something I prefer not to use.

Updated

Here it goes the test description. First I modified the original code to use Class::Virtual in the Animal class:

package Animal;
use base qw(Class::Virtual);
use strict;
use warnings;

sub new {

    my $class = shift;

    # hash reference
    my $self = shift;
    bless $self, $class;
    return $self;

}

__PACKAGE__->virtual_methods(qw(get_sound get_color));

1;
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Then I changed the test.pl script:

use strict;
use warnings;
use Animal::Dog;
use Animal::Duck;

my $dog  = Animal::Dog->new(  { name => 'Atila' } );
my $duck = Animal::Duck->new( { name => 'Donald' } );

print $dog->get_name(),  ' says ', $dog->get_sound(),  "\n";

my @missing = Animal::Duck->missing_methods();
warn 'Animal::Duck forgot to implement ' . join ', ', @missing if @mis
+sing;

print $duck->get_name(), ' says ', $duck->get_sound(), "\n";
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Finally, the results:

C:\>test.pl
Atila says "bark bark!"
Animal::Duck forgot to implement get_sound at C:\test.pl line 12.
Animal::Duck forgot to implement get_sound() at C:\test.pl line 14
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While using the method virtual_methods looks more simple to use than having to type several times sub something :Abstract the module forces you to use more code (using the missing_methods method) just to check if you didn't forgot something.

I think I'll change the Attribute::Abstract to use something like virtual_methods: while using Attribute::Handlers looks fancy, is not really necessary.