Yeah, if you've got a version of Perl that supports such. Way too many versions of Perl after \d began including Klingon^* digits yet before /a was implemented.

Plus, /a messes with more than just \d. I have yet to run into a single project I was involved in where a string of Klingon^* digits would be correctly parsed as a numeric value. But I've touched plenty of projects where \w including more letters than a-z was quite useful. Perl itself is that way, after all. Sure, you could write (?a:\d) but that's just longer and less clear (and less portable).

So I suspect I'll be sticking with [0-9] for quite a while still.

^* No, Unicode doesn't actually include Klingon (yet, anyway).