(?P>name) Recurse into a named subpattern (python syntax)
(?(cond)yes|no)
(?(cond)yes) Conditional expression, where "cond" can be:
- (?=pat) look-ahead
- (?!pat) negative look-ahead
- (?<=pat) look-behind
- (?<!pat) negative look-behind
+ (?=pat) lookahead
+ (?!pat) negative lookahead
+ (?<=pat) lookbehind
+ (?<!pat) negative lookbehind
(N) subpattern N has matched something
(<name>) named subpattern has matched something
('name') named subpattern has matched something