do and multiple values

gistfile1.lisp

(defmacro do-mvb (var-bindings end-and-result &body body)
  (let* ((bindings nil)
         (first-time-p (gensym))
         (var-bindings-
          (reduce (lambda (result binding)
                    (if (consp binding)
                        (destructuring-bind (value . form) binding
                          (cond ((consp value)
                                 (push (cons value form) bindings)
                                 (append result value))
                                (t (append result (list binding)))))
                        binding))
                  var-bindings
                  :initial-value (list `(,first-time-p t nil)))))
    `(do ,var-bindings-
         ,end-and-result
       ,@(mapcar (lambda (binding)
                   `(if ,first-time-p
                        (multiple-value-setq ,(car binding) ,(cadr binding))
                        ,(if (caddr binding)
                             `(multiple-value-setq ,(car binding)
                                ,(caddr binding)))))
                 bindings)
       ,@body)))