On Jan 24, 2011, at 6:51 PM, Charles Turner wrote: > Tried things like: > >> begin = '(?<=0\s+:\s+0$)'; "Subexp of look-behind must be fixed character length. But different character length is allowed in top level alternatives only. ex. (?<=a|bc) is OK. (?<=aaa(?:b|cd)) is not allowed." C.