The author of Boost is quite right. Perl doesn't have a standard, and regexes in Perl6 will be different (although there's a promise Perl5 style regexes will work as well).

Read about the Perl6 regexes in Apocalypse 5: Pattern Matching.

There's no book about Perl6 regexes yet - but no doubt O'Reilly or some other publisher is willing to publish one as soon as someone can convince them they could write a good book about them. (Perl publishers will be very happy with Perl6 - it gives them the opportunity to sell their books again).