The term "regex" usually means not "regular expressions" in the formal languages sense but rather the trickier operational notion that makes use of backtracking

The term "regex" usually means not "regular expressions" in the formal languages sense but rather the trickier operational notion that makes use of backtracking. Look at http://cstheory.stackexchange.com/questions/448/regular-expressions-arent http://cstheory.stackexchange.com/questions/448/regular-expr...