the more natural ordering of your arguments would be ($lchompstr, $optional_string_arg)

In hindsight you are right. Unfortunately we already have other functions in use, which have the ordering in the way may lchompx is going to be used, and I don't know yet whether I'll have the nerves to change all these consistently. Maybe I'll do one day, and certainly I would do it in the way you propose, if I had to develop all this again.