Select Code to Download

 $app->add_event_handler(sub {
        my $event= shift;
        if($event->type == SDL_KEYDOWN){
...
            }
        }
});

use strict; 
...
    $ball->{v_x} = (4 + rand(2)) * (rand (2) > 1 ? 1 : -1);
    $ball->{v_y} = (1.5 + rand(1)) * (rand (2) > 1 ? 1 : -1);        
}