> On the subject of \b I'll note we do have \W and \w 

So we do, I overlooked that. And we define it a little differently from
Perl:

[#x0000-#x10FFFF]-[\p{P}\p{Z}\p{C}] 

So for example "+" is regarded as part of a word, while "-" isn't. Which
strikes me as totally useless, to be honest.

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay