(define (foo x y)
  (if (and (eq? (##sys#slot x 0) y)
           (eq? (##sys#slot x 0) y))
      (##sys#slot x 0)
      (if (and (eq? (##sys#slot x 0) y)
               (eq? (##sys#slot x 0) y))
          (##sys#slot x 0)
          (if (and (eq? (##sys#slot x 0) y)
                   (eq? (##sys#slot x 0) y))
              (##sys#slot x 0)
              (if (and (eq? (##sys#slot x 0) y)
                       (eq? (##sys#slot x 0) y))
                  (##sys#slot x 0)
                  (fail))))))

(foo 123)
(foo 456)

;; csc -O2 -d0 -debug 7 -A x.scm