-----test.pl-------
use Cat;

$mycat = cat->new();
$mycat->feed("fish");
exit;


-----Cat.pm-------
package Cat;

use strict;
use warnings;
our $VERSION = '0.01';
our @ISA = ();


sub new
{
    my $class = shift;
    my $self = { Stomach => "empty" }; 
    bless $self, $class;
    return $self;
}
sub feed
{
   my ( $self, $food ) = @_;
   $self->{ Stomach } = $food if defined $food;
   return $food;
}

1;
__END__