Last night I released version 0.8 of regexp-engine(perl5+6), which I have been on its way for a long time (4 months). I finally got fixed a very peculiar problem with nested quantifiers and backtracking. Besides that I got hit by the

premature optimization is the root of all evil

so that took a great piece of my time. Theres a testsuite (Rubicon) which exercises many aspects of Ruby, it contains 1560 tests of Ruby's native regexp engine. My initial goal has been to be compatible with 95% of these tests, which I have now exceeded. For a really long time I were only able to do 92% of the tests, and now I do 96.025% so I am very satisfied. But I guess its another example of the 80-20 rule:

The last 20 percent, takes 80 percent of the time

I like perl6 regexps, How about you?