[Guido & Andrew on Tcl's new regexp code]
I'm sure that if it's good code, we'll find a way. Perhaps a more interesting question is whether it is Perl5 compatible. I contacted Henry Spencer at the time and he was willing to let us use his code.
Haven't looked at the code, but did read the manpage just now: http://www.scriptics.com/man/tcl8.1/TclCmd/regexp.htm WRT Perl5 compatibility, it sez: Incompatibilities of note include `\b', `\B', the lack of special treatment for a trailing newline, the addition of complemented bracket expressions to the things affected by newline-sensitive matching, the restrictions on parentheses and back references in lookahead constraints, and the longest/shortest-match (rather than first-match) matching semantics. So some gratuitous differences, and maybe a killer: Guido hasn't had much kind to say about "longest" (aka POSIX) matching semantics. An example from the page: (week|wee)(night|knights) matches all ten characters of `weeknights' which means it matched 'wee' and 'knights'; Python/Perl match 'week' and 'night'. It's the *natural* semantics if Andrew's suspicion that it's compiling a DFA is correct; indeed, it's a pain to get that behavior any other way! otoh-it's-potentially-very-much-faster-ly y'rs - tim