in reply to
Re^2: How to use \l and \u in regex mathing patterns?
in thread How to use \l and \u in regex mathing patterns?
I don't think it was a hack, ugly or otherwise. I think it was intended, and succeeds, as an example of the actual way interpolation control operators can work in a regex, which was the context of the original – albeit misguided, since pat_mc thought of them as character classes – question. (Although I must admit that, had I given the example myself, I might have mentioned that those operators are rarely used in that particular way.)