(define fail-tag 'temp)
(call/cc (lambda (top-level)
  (set! fail-tag top-level)))
 
(define (fail) 
  (fail-tag 'failed))
 
(define (choose . options)
  (if (null? options)
      (fail)
      (call/cc (lambda (success)
        (let ((old-fail fail-tag))
          (call/cc (lambda (new-fail)
            (set! fail-tag new-fail)
            (success (car options))))
          (set! fail-tag old-fail)
          (success (apply choose (cdr options))))))))
 
 
 (let () 
 	(display (list (choose 'a 'b 'c) (choose 1 2 3)))
 	(fail))
 

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