( queue
  =   (list=)
      (enqueue=.(.!arg) !(its.list):?(its.list))
      ( dequeue
      =   x
        .   !(its.list):?(its.list) (.?x)
          & !x
      )
      (empty=.!(its.list):)
  )
& new$queue:?Q
& (   (Q..enqueue)$1
    & (Q..enqueue)$2
    & (Q..enqueue)$3
    & out$((Q..dequeue)$)
    & (Q..enqueue)$4
    & out$((Q..dequeue)$)
    & out$((Q..dequeue)$)
    &   out
      $ ( The
          queue
          is
          ((Q..empty)$&|not)
          empty
        )
    & out$((Q..dequeue)$)
    &   out
      $ ( The
          queue
          is
          ((Q..empty)$&|not)
          empty
        )
    & out$((Q..dequeue)$)
    & out$Success!
  | out$"Attempt to dequeue failed"
  )
;