where.el

(defmacro lwt (&rest args)
  (destructuring-bind (b1 wh b2 &rest body) args
    `(let* (,@b2 ,@b1) ,@body)))

(macroexpand-all
 '(lwt ((w (* x y)))
       :where
       ((x 2)
        (y 3))
       (+ 1 w)))

(lwt ((w (* x y)))
     :where ((x 2)
             (y 3))
     (+ 1 w))