There is the \# character, which is replaced with the number of times a replacement has been done. So, M-x replace-regexp Replace regexp: test\(.+\)

There is the \# character, which is replaced with the number of times a replacement has been done. So, M-x replace-regexp Replace regexp: test\(.+\) Replace regexp with test\# You can actually drop arbitrary lisp in the middle of search/replace expressions. So, if you'd like to number from 1 instead of 0, M-x replace-regexp Replace regexp: test\(.+\) Replace regexp with test\,(1+ \#\) I'm sure with more lisp tricks, you can get delimited lists: M-x replace-regexp Replace regexp: test\(.+\) Replace regexp with test\,(aref ["one", "two", "three"] (mod \# 3)) (Not sure that works, but you get the idea). Anyway, all of this was basically stolen from Steve Yegge. You should totally go read his article if you're interested: http://steve-yegge.blogspot.com/2006/06/shiny-and-new-emacs-22.html http://steve-yegge.blogspot.com/2006/06/shiny-and-new-emacs-...