Here's a (brief) explanation on how this works. When the detector realizes a key (ANY key) is pressed, it repeats a key check the amount of items in (list) keys. If the key check results in a key which is placed in the (list) keys, it outputs the message: Key [key pressed] pressed. Btw, the more keys to detect, the more frames it takes to detect keys.
100% by @-Voxel- (me).