All the sources codes "But why ?"page 32

public void swap(Object a, Object b) {
    Object temp = a;
    a = b;
    b = temp;
}

if !if object_exists(facebook_app) {instance_create(x+0,y+0,facebook_app)} other if object_exists(facebook_app) {with(facebook_app) instance_destroy();}

// Replaces with spaces the braces in cases where braces in places cause stasis 
$str = str_replace(array("\{","\}")," ",$str);