(setq regex-1 ".*?mul(\\([[:digit:]]\\{1,3\\}\\),\\([[:digit:]]\\{1,3\\}\\))")

(setq regex-2-1 ".*?\\(mul([[:digit:]]\\{1,3\\},[[:digit:]]\\{1,3\\})\\|don't()\\|do()\\)")

(defun try-regex-part1 ()
  (replace-regexp regex-1 "\n(* \\1 \\2);"))

(defun try-regex-part2 ()
  (interactive)
  (goto-char (point-min))
  (replace-regexp regex-2-1 "\n\\1") ;remove most of the broken code
  (kill-line) ;remove the rest of the broken code
  (goto-char (point-min))
  (replace-regexp "do()" "do")
  (goto-char (point-min))
  (replace-regexp "don't()" "dont")
  (goto-char (point-min))
  (replace-regexp regex-1 "(* \\1 \\2)")
    (goto-char (point-min))
    (insert "(")
    (goto-char (point-max))
    (insert ")")
  )

;; the above turns the input into some pseudo lisp code. the code is then executed by the sexp below

(-reduce-from (lambda (i e) (cond
                             ((eq e 'do) `(t ,(cadr i)))
                             ((eq e 'dont) `(nil ,(cadr i)))
                             (t (if (car i) `(t ,(+ (cadr i) (eval e)))
                                  `(t ,(cadr i))))))
              '(t 0) code))

; this is quite horrible, and probably there is a more efficient way