(set-cdr! pair argument)) -> pair
Destructively replaces the cdr, or everything except the first element, of a pair or list with the second argument, and returns #f. In order to access the pair again, it is best to first have stored it as a symbol, so it can be called.
To continue the example from set-car!:
song (after set-car!) returns (Alice had a little lamb)
>>(set-cdr! song '(went down the rabbit hole)) :: #f
>>song :: (Alice went down the rabbit hole)
See Also: set-car!