Ask HN: A tool that helped iterate over command line arguments

Hello-

A few days back I saw a tool that helped you iterate over the arguments to previous commands in a straightforward way. I can't seem to find it. Does anybody remember what it was?

My impression of it was, say your session goes like this:

$ ls x y z $ ls a b c $ dir a b $ cp <hit something to go over arguments>

Now I know Alt-. can do such a thing but the tool seemed easier...