&rest lists - correction

[mcvax!pilatus!ceb@uunet.UU.NET]

In my previous posting, the counter example should have read 
(setf (cdar ..) .), since (setf (cadr ..) .) *would* be covered by
backbone copying.  Hope this didn't cloud things.

I grow rusty on "under-the-hood tinkering", since I now use mainly
semantically cleaner defstructs.