Named captures are a great way to document your regular expressions. Don't use the "#" notation to comment on what the regex is doing, just name the group instead!

.Net has had them for a long, long time and they are AWESOME!

It'd be cool to see Ruby get something like a MatchEvaluator, too

http://msdn.microsoft.com/en-us/library/system.text.regulare...

A MatchEvaluator lets you much more complicated regex find replace. Currently, find/replace only lets you re-order or remove groups or insert static text. A MatchEvaluator lets you handle what to replace the match with code - meaning you can call a webservice that will replace MM/DD/YY with the equivalent Mayan/Persian/Lunar date.