[asicsp]

That was changed recently, I get 'xbxcx' on 3.5 and 'xbxxcx' on 3.7

And coming to Perl vs Python regex differences, there are too many to count, Python's 3rd party module 'regex' is more comparable to Perl regex. For example, Python doesn't support possesive quantifiers, subexpression calls, \K, \G and so on