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

package Top;

sub new {
    my ($class, %params) = @_;
    my $self = bless \%params, $class;
    return $self;
}

sub firstSub {
    my ($class) = @_;
    print "FIRST SUB!\n";
}

package Top::Extend1;

push @Top::ISA, 'Top::Extend1';

sub addOnSub {
    my ($self) = @_;
    print "ADD ON\n";
}

package Top::Extend2;

push @Top::ISA, 'Top::Extend2';

sub secondAddOn {
    my ($self) = @_;
    print "SECOND ADD ON\n";
}

package main;

my $test = Top->new();

$test->firstSub();
$test->addOnSub();
$test->secondAddOn();