package Robo;
use strict;
use warnings;

sub new {
    bless {
        Arm => Robo::Arm->new(),    # 'Arm' points to instance of Robo::Arm
        Feet => Robo::Feet->new(),   #'Feet' points to instance of Robo::Feet
    }, shift    
}

1;
 
package main;
 
my $robo = Robo->new();
$robo->{Feet}->walk();
$robo->{Arm}->pick( "Apple" );