I dunno, the "logic" solution seems like the obvious one to me; if your boss really has that much trouble with propositional logic that they don't immediately see why it works, well, that's what code comments are for.

(...the trick is still cool, though; I can imagine other situations where it would be more useful. However it does seem like it potentially depends on the particular regex engine being used, in contrast to the author's claim about it being totally portable; yes, it'll compile on anything, but will it work?)