package View; 
 
use strict; 
use warnings; 
use 5.010; 
 
sub new { 
    my $self = {}; 
 
    $self->{OUTPUT} = undef; 
    $self->{INPUT} = undef; 
 
    bless $self; 
    return $self; 
} 
 
sub display_output { 
    my $self = shift; 
    $self->{OUTPUT} = shift; 
         
    say "computer says: $self->{OUTPUT}"; 
 
    return undef; 
} 
 
sub retrieve_input { 
    my $self = shift; 
 
    print 'your response: '; 
    $self->{INPUT} = <STDIN>; 
 
    return $self->{INPUT}; 
} 
 
return 1;

package Controller; 
 
use strict; 
use warnings; 
use 5.010; 
 
sub new { 
    my $class = shift; 
    my $self = {}; 
     
    $self->{VIEW} = shift; 
    $self->{MODEL} = shift; 
 
 
    bless $self; 
    return $self; 
} 
 
sub interact_with_user { 
    my $self = shift; 
    my $output = shift; 
 
    $self->{VIEW}->display_output($output); 
    $self->{VIEW}->retrieve_input; 
 
    my $response_count = $self->{MODEL}->calculate_response_count(1); 
 
    $output = "total responses = $response_count"; 
    $self->{VIEW}->display_output($output); 
     
    return undef; 
} 
 
return 1;

     
package Model; 
 
use strict; 
use warnings; 
use 5.010; 
 
sub new { 
    my $self = {}; 
 
    $self->{RESPONSE_COUNT} = 0; 
 
    bless $self; 
    return $self; 
} 
 
sub calculate_response_count { 
    my $self = shift; 
    my $increment = shift; 
     
    $self->{RESPONSE_COUNT} += $increment; 
 
    return $self->{RESPONSE_COUNT}; 
} 
 
return 1;

use strict; 
use warnings; 
use 5.010; 
 
use Model; 
use View; 
use Controller; 
 
 
my $view = View->new(); 
my $model = Model->new(); 
my $controller = Controller->new($view, $model); 
 
$controller->interact_with_user('hello');