Select Code to Download

sub default_code {
    my ($self,$extra) = @_;
    my $sub = sub { 
...
        };
    return $sub;
}

$object->display( { my_code => sub { 
                        my ($hashref) = shift;
...
                             }; 
                   }
                 );

sub display {
   my ($self,$args) = @_;
...
   my $action = $args->{'my_code'} || $self->default_code;
   $action->($args);
}