I think you are looking at it from the wrong perspective. You could do what you are doing by starting a timer, which runs a loop, when a key is pressed, then stop the loop when the key is released, but that is alot of trouble.

I would just set a certain amount of "motion ( dx or dy )" to each key press, and set up a "repeat interval for the keys"). So when you hold the key down, you will get a succesion of events, which stop when the key is released.

Here is a super simple example just to give you the idea. Instead of printing the repeating key code, just assign your motion.

#!/usr/bin/perl
use SDL::App;
use SDL::Event;
use SDL;

### Create A new Application window 
my $app = new SDL::App
-width => 400,
-height => 400;

### A simple event handler hash 
my $events = {

SDL_KEYDOWN() => sub {
        my ($e) = @_;
        exit(0) if ( $e->key_sym() == SDLK_ESCAPE );
        print $e->key_sym(),"\n";
    },

   SDL_QUIT() => sub { exit(); },
};

my $eventkr = new SDL::Event;
$eventkr->set_key_repeat( 10, 10);


### Loop & process the events 
$app->loop($events);
#$app->loop(); #no events, must kill to exit
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