I have no idea why that regsubex shortcut is so popular when it can only support small channels. Mircs string limit is 4000 and something chars, so that script wouldn't work in a 100 user channel if everyone had nicknames only 5 characters long. A lot of nicks are longer than that, so in reality it will crap out on considerably smaller channels.

Just use a while loop. It may be longer but it's more suitable for the task at hand. We should never sacrifice functionality just to have a smaller script.