; New Sealer Pair (fails!!)
(define (NSP) (let ((Br (cons 0 0))) (cons (lambda (x)
  (lambda (b) (if (eq? b Br) x 42))) (lambda (p) (p Br)))))
(define x (NSP))
(define seal (car x))
(define uns (cdr x))
(uns (seal 48))
; downfall:
(uns (lambda (y) (set! x y)))