Afaik Python, like most open source languages, use the PCRE lib, Perl Compatible Regular Expressions. Google it.

PCRE isn't as good as Perl's regexps, but not bad. (I've helped people with PCRE problems that worked in Perl.)

Edit: I googled myself. :-) The Python lib isn't pcre (anymore), it is something home rolled. The answer to the parent question about inspiration is: Most everyone has copied the Perl syntax (except, irritatingly, Emacs).

Edit 2: herge -- Perl is ~ a superset of awk. Use that. (Check -n and -e flags in perldoc perlrun.)