Having issues with resizing my SDL::App

Hi

I'm currently working on a simple game.

But now I'm trying to resize the SDL::App windows by using the following
code

my $app = new SDL::App(
    -title=>$title,
    -width=>800,
    -height=>600,
    -depth=>32,
    -flags=>SDL_DOUBLEBUF | SDL_HWSURFACE | SDL_HWACCEL,
    -resizeable,
);

$newx=640;
$newy=480;

$app->resize($newx, $newy);


But this wont work
Are there any other steps required?

Dennis