(define $main
  (lambda [$argv]
    (match argv (list string)
      {[<nil> (letrec {[$iter
                        (do {[$eof (eof?)]
                             [(unless eof
                                (do {[$line (read-line)]
                                     [(write-string line)]
                                     [(write-char '\n')]
                                     [iter]}
                                  []))]}
                          [])]}
                iter)]
       [_ (cat-files argv)]})))

(define $cat-files
  (match-lambda (list string)
    {[<nil> nop]
     [<cons $file $files>
      (do {[$port (open-input-file file)]
           [(letrec {[$iter
                     (do {[$eof (eof-port? port)]
                          [(unless eof
                             (do {[$line (read-line-from-port port)]
                                  [(write-string line)]
                                  [(write-char '\n')]
                                  [iter]}
                               []))]}
                       [])]}
              iter)]
           [(close-input-port port)]
           [(cat-files files)]}
        [])]}))

(define $nop
  (return []))

(define $when
  (lambda [$cond $action]
    (if cond action nop)))

(define $unless
  (lambda [$cond $action]
    (when (not cond) action)))