Life

> (define saved-cont #f)
> (call-with-output-file* "file.txt" (lambda (out)
                                       (let/cc cont (set! saved-cont cont))
                                       (fprintf out "hello\n")) #:exists 'append)
    
> (saved-cont)
fprintf: output port is closed

> (call-with-continuation-barrier
   (lambda ()
     (call-with-output-file* "file.txt" (lambda (out) (let/cc cont (set! saved-cont cont))
                                         (fprintf out "hello\n")) #:exists 'append)))                                 
> (saved-cont)
continuation application: attempt to cross a continuation barrier