cat.rkt

(define-syntax cat
  (syntax-rules ()
    [(cat (str . args))
     (format str . args)]
    [(cat (str . args) (str2 . args2) ...)
     (string-append
      (cat (str . args))
      (cat (str2 . args2) ...))]))

(define-syntax orz
  (syntax-rules ()
    [(orz . body)
     (error (cat . body))]))