I think you have to have dotted pairs for that.
AutoLISP only knows one type of data structure: the linked list.
It's the type of elements in the list that allows it to be used as a matrix, a tree, an association list and so on.
Any list whose every items are lists can be used as an association list.
The use of dotted pairs element of the association lists makes it possible to maintain coherence for the treatment of such lists as "dictionaries": you can use cdr to get the value of the 'key' entry that either a list or an atom: (cdr (assoc key lst)).
'(
(10 5. 3. 0.)
(1 . "foo")
(2 "bar")
)
)
alst is an association list because you can get each element using (assoc ...).
(cdr (assoc 10 alst)) returns (5.0 3.0 0.0)
(cdr (assoc 1 alst)) returns "foo"
but:
(cdr (assoc 2 alst)) returns ("bar") which is a list, we have to use (cadr (assoc 2 alst)) to get the value.