OTOH, multiple attempts by multiple groups to steal Perl's regexp engine years ago fizzled out in a tarpit of frustration.
Oh, I had the impression that Python's re *was* pilfered Perl.
Tim warned me that the mere attempt to read sources for existing RE implementations was a sure way to destroy my brain, so I avoided that.
SRE is a clean-room implementation, using the Python 1.5.2 docs and the regression test suite as the only reference. I've never written a Perl regexp in my life.