tokens would work... though it'd have to be something like $fortok(<variable>,<start>,<end>,<C>,<command>)
I searched... I didn't find anything...
EDIT: I searched again, and found old posts dealing with it. Mostly, there were objections relating to being able to do it with a while loop. One objection mentioned that a "$loop(<number>,<command>)" identifier wouldn't be useful because they almost always want to use multiple commands in the loop.
I wrote the scripts at http://paste.sarten-x.com/pastebin.pl?number=85
for fun, and all the ones that use $regsubex($str... could all be simplified greatly using a $for.
OTHER EDIT: It should be said that those scripts were written with the intent of using a single command to do the task. They also were written mostly after 3:00 AM.