The /b behaviour is inconsistent, and I don't think we should be supporting it indefinitely. We should abandon it entirely. The /a, /u, and /l behaviours are all sane, and if the meaning of \w et al are going to be variable then modifiers are the right way to do it. As for what should be the default: apparently the rationale for having variable meaning is that it's too much trouble to change all the code that's expecting Unicode behaviour, so the only sensible default in that case is /u. I suppose this means that we're resigned to amending all the existing code that wants ASCII behaviour, which is funny because I thought there was a lot more code in the latter category than the former. If changing Unicode-based code is *not* too onerous, I'd favour /a being the default, and possibly not doing the modifier thing at all.