Looking at the wiki, I don't think it does handle them. I reckon that if jehna when to the trouble of making this, he knows of at least one use case, even if it's his own. I appreciate that he's shared his work. That said, from my own experience, by the time a regular expression becomes difficult for me to parse, there are subexpressions, negative lookbehinds, and other less comprehensible regex features that this library doesn't seem to support.