We may be running afoul of differing or overlapping definitions of the meanings of words like 'advanced' and 'extended'. If 'advanced' is more or less synonomous with 'extended', then look-arounds are, as described in the quoted section of perlre, advanced anent awk- and lex-ish usage.

I think 'advanced', in this context, has more to do with words like 'complicated', 'subtle', 'non-intuitive' or 'counter-intuitive'. To me, look-arounds are pretty straightforward and intuitive (except for the fixed-width limitation of look-behinds), thus not advanced at all. I also think that look-arounds fall squarely under the 'part of the core language for many years' rubric of the quoted perlre section, and are not likely to change their behavior for the future of Perl 5.

Given that look-arounds are mature, stable and straightforward, it is well to commend regex tyros (as ultranerds seems to be) to their familiarity and use. Alternatives and multiple cat-skinning methods are fine (and I agree that the OPer is the final arbiter), but they should not obscure expressive and stable features of the language from which newcomers may benefit.

My personal experience is that pretty much all regex behavior is one or more of complicated, subtle, and non- or counter-intuitive (and that applies to the approach taken in your example code), so no expressive, stable extension should ever be shunned.