Thanks very much. It turns out the first one can be called with multiple args in the "expr" slot, so it has to be

    (defmacro defsmac (name params &rest expr)
      `(defmacro ,name ,params
         `,(cons 'progn (sublis (mapcar 'cons ',params 
                (list ,@params)) ', expr))))

but your code got me un-stuck.