I haven't Forthed in a long time, but you can write variadic words (e.g., "keep popping until a negative number is reached"). You just (a) shouldn't, probably;

I haven't Forthed in a long time, but you can write variadic words (e.g., "keep popping until a negative number is reached"). You just (a) shouldn't, probably; and (b) can't document their stack effect properly.