Unicode property <:cntrl>
This feature is meant to mimick TheDamian's Regexp::Grammars. The present commit is only a first cut in that direction. More precisely, this commit creates a somewhat similar output, but doesn't yet attempt to mimick the CPAN module's output in exact detail.
This is a bit of an ego commit; I tend to have a fairly bleeding perl6 implementation in /usr/local/bin/perl6. Since that's now the newly merged 'ng' branch, which can't yet run GGE, I choose to invoke the 'old master', which I keep at /usr/bin/alpha on my computer. YMMV.
This was possibly the hardest single commit so far, in terms of the time it took and the thinking it required. Especially since it doesn't do very much. A 'before' subrule call anchors the match at that point, checks if it matches, and returns either a failed match or a zero-width successful match.
Putting all your previous calculations into a global hash is something that the GC tends to frown upon. This (de-)optimisation relies on the fact that the same regex is often repeated in contiguous regions, and thus only the last regex need be cached.