S9 LIB  (let/cc <name> . <body>)  ==>  object

        (load-from-library "letcc.scm")

Bind the current continuation to <name> and evaluate <body> with
that binding in effect. 

(let/cc exit
  (letrec
    ((f (lambda (x)
          (cond ((null? x) 0)
                ((pair? x) (+ 1 (f (cdr x))))
                (else      (exit 'foo))))))
    (f '(1 2 3 . 4))))                         ==> foo
