package CirculatorySystem;
use Moose;

has 'pressure' => (is => 'ro', isa => 'HashRef[Int]');

package Eyes;
use Moose;

has 'body' => (
    is       => 'rw',
    isa      => 'Body',   
    weak_ref => 1, # cycles are bad 
    handles  => [qw[ blood_pressure ]]
);

package Body;
use Moose;

has 'circulatory_system' => (
    is      => 'ro',
    isa     => 'CirculatorySystem',   
    handles => {
        blood_pressure => 'pressure'
    }
);

has 'eyes' => (
    is      => 'ro', 
    isa     => 'Eyes',
    trigger => sub {
        my $self = shift;
        # must hook up new eyes 
        # to the body ...
        $self->eyes->body($self);
    }
);

package main;

my $nexus_6 = Body->new(
    eyes               => Eyes->new, # i make your eyes!
    circulatory_system => CirculatorySystem->new(
        pressure => { systolic => 112, diastolic => 64 }
    ),
);


print $nexus_6->blood_pressure; 
# is the same as ...
print $nexus_6->circulatory_system->pressure;
# is the same as ...
print $nexus_6->eyes->blood_pressure;

##</code><code>##

has [qw[ eyes ears nose mouth ]] => (is => 'rw');
around [qw[ eyes ears nose mouth ]] => sub { ... code to make accessors return $self here ... }

##</code><code>##

my @parts = qw[ eyes ears nose mouth ];
has $_ => (
    is        => 'rw',
    predicate => "has_$_"
) foreach @parts;