The joke lies in interpreting human languages as if it was a computer algorithm. Remove any computer language context, and it is hard to even find a joke or logic in this. Any human would not do this interpretation since we can understand context, this would only be seen as a very strange attempt at a joke. However, computers don’t understand context, so adding that component and the joke makes sense. So, even if it really is a grammar joke, it needs the programming context to work as a joke.