[megaframe]

Oddly enough I was asked once to determine if there were any differences between Perl Regex and Python's implementation in an effort to convert a tool I wrote into Python (so other developers could help)

I found only one very weird edge case worth noting, in Perl the regex "s/ a* / x /g" (spaces added to prevent formatting) will turn the string "bac" into "xbxxcx" because the "a" technically means zero or more so it matches the spaces between the characters, not so in python it creates the string "xbxcx" because it matched the a in between one time and didn't count the empty spaces. Slightly less accurate results since * does mean zero or more so the space between counts as zero characters.

[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