stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownHandler);
stage.addEventListener(KeyboardEvent.KEY_UP, keyUpHandler);

function keyDownHandler(e:KeyboardEvent):void {
	switch (e.keyCode) {

	case Keyboard.LEFT :
		//left=true;
		rotleft=true;
		break;

	case Keyboard.RIGHT :
		//right=true;
		rotright=true;
		break;

	case Keyboard.UP :
		forward=true;
		break;

	case Keyboard.DOWN :
		back=true;
		break;

	case  87 :
		forward=true;
		break;

	case 83 :
		back=true;
		break;

	case Keyboard.ENTER :
		restart=true;
		break;

	case Keyboard.SPACE :
		shoot=true;
		break;
	}
}

function keyUpHandler(e:KeyboardEvent):void {
	switch (e.keyCode) {

	case Keyboard.LEFT :
		//left=true;
		rotleft=false;
		break;

	case Keyboard.RIGHT :
		//right=true;
		rotright=false;
		break;

	case Keyboard.UP :
		forward=false;
		break;

	case Keyboard.DOWN :
		back=false;
		break;

	case Keyboard.SPACE :
		shoot=false;
		break;


	case Keyboard.ENTER :
		restart=false;
		break;


	case  87 :
		forward=false;
		break;

	case 83 :
		back=false;
		break;
	}
}

function moveBall(evt:Event) {

	if (forward) {
...
}
}