KeyObject.as von senocular
http://www.senocular.com/flash/actionscript/?file=ActionScript_3.0/com/senocular/utils/KeyObject.as

"The KeyObject class recreates functionality of Key.isDown of ActionScript 1 and 2.
 Usage:
   var key: KeyObject = new KeyObject(stage);
   if (key.isDown(key.LEFT)) { ... }
"