Something

(defun find-in-env (symb env)
  (let ((cell (assoc symb env))) 
    (if cell 
        (cadr cell)
        symb
    )
  )
)

(defun replace-vars (expr env)
   (if (consp expr)
       (mapcar #'(lambda (x) (replace-vars x env)) expr)
       (find-in-env expr env)
   )
)

(defun meval-body (expr env)
   (eval (replace-vars expr env)
   )
)