ANSI Common Lisp 5 Data and Control Flow 5.1 Generalized Reference 5.1.2 Kinds of Places
18.104.22.168 VALUES Forms as PlacesA values form can be used as a place, provided that each of its subforms is also a place form.
A form such as
(setf (values place-1 ... place-n) values-form)
does the following:
The storing form in the setf expansion of values returns as multiple values2 the values of the store variables in step 2. That is, the number of values returned is the same as the number of place forms. This may be more or fewer values than are produced by the values-form.