package Example::Phone {
  use Moo;
  has number => (is => 'ro', required => 1);
  sub call { ... }
}

##</code><code>##

use Example::Phone;

my $dad = Example::Phone->new(number => '+44 123 456 7890');
say "Dad's number is ", $dad->number;
$dad->call();

##</code><code>##

package Example::Phone::Mobile {
  use Moo;
  extends 'Example::Phone';
  sub send_sms { ... }
}