package A;

use strict;

use fields qw(id name);

sub new {
 ...
}

##</code><code>##

package B;

use strict;

use base qw(A);
use fields qw(addr phone city);

##</code><code>##

package C;

use strict;

use base qw(A);
use fields qw(model type);

##</code><code>##

use C;