(defmacro save-place ((place &optional new) &body body &environment env)
  (multiple-value-bind (vars vals store-vars writer-form reader-form) (get-setf-expansion place env)
    (when (cdr store-vars) (error "Can't expand this place ~S" place))
    (let ((name (gensym)))
      `(let* (,@(mapcar (function list) vars vals)
              (,(car store-vars) ,reader-form))

         (let ((,name (or ,new ,(car store-vars))))
           (unwind-protect (progn ,@body)
             (setf ,(car store-vars) ,name)
             ,writer-form))))))

(let ((k (vector (cons 42 33)
                 (cons 0 0)
                 (cons 1 1)))
      (i -1))
  (block out
    (save-place ((car (aref k (incf i))))
      (dotimes (j (length k))
        (setf (car (aref k j)) -1
              (cdr (aref k j)) -1))
      (return-from out 'hi)))
  (assert (= 42  (car (aref k 0))))
  k)
; --> #((42 . -1) (-1 . -1) (-1 . -1))