Not sure why that header is included there, though. I can't find any uses of the regex library. There are multiple custom matchers implemented. So maybe it's that the GNU regex library uses the grep sources. In any case, there don't seem to be any uses of regexec() or regcomp(), for example. Which would have surprised me anyway since that API is rather limiting (you cannot search incrementally).

Let's get that beer sometime, anyway.

I was saying "canned", not "boxed" or "containerized". It's a lot easier to write the little things yourself. (And there are good benefits to be had from writing specialized code yourself, instead of relying on big fat generalized tankers.)