package Father;
use warnings;
use strict;

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


# INTERFACE
sub aText {
  #implement
  die('Parent aText');
}

sub aList {
  # implement
  die('Parent aList');
}
1;

##</code><code>##

package Son;
use warnings;
use strict;

use Father;
use base qw(Father);

use constant {
  aText => 'This is a Text',
  aList => [qw(aaa bbb ccc)],
};

sub print_son {
  my $self = shift;  
  print 'Son:', $self->aText(), "\n";
  print 'Son: ', join(', ', @{$self->aList()}), "\n";
}

1;

##</code><code>##

#! /usr/bin/perl
use strict;
use warnings;


use Son;

my $s = Son->new();
print $s->aText(), "\n";
print join(', ', @{$s->aList()}), "\n";

$s->print_son();