(define (mdalconfig-proc #!key version target (description "a default description") commands input output)
  (unless (= version 2)
    (error "Version is wrong"))
  (print "target is: " target)
  (print description)
  #;(do-whatever commands input output))

(define data (with-input-from-file "data" read))

;; You can replace this if with a hash-table lookup
;; if you have multiple commands, for example.
(if (and (pair? data)
         (eqv? (car data) 'mdalconfig))
    ;; this is where the magic happens
    (apply mdalconfig-proc (cdr data))
    (error "unknown configuration command"))