anchor.diff:  -export([init/1, handle_call/3, handle_cast/2,
            handle_info/2, code_change/3, terminate/2]).
   
  --record(state, {key, ctrl, opts}).
  +-record(state, {key, ctrl, opts, mon_ref}).
   
   %% Management Api -------------------------------------------------------------
   
  
positive.code: %% gen_server callbacks -------------------------------------------------------
  
  init([Key, Ctrl, Opts]) ->
      {ok, #state{key=Key, ctrl=Ctrl, opts=Opts}, 0}.
  
  handle_call(_, _, State) ->
      {noreply, State}.
  
negative.code:             Ctrl ! {watch, self(), Response},
              {stop, normal, State}
      end;
  handle_info({'DOWN', MonRef, _, _, _}, #state{mon_ref=MonRef} = State) ->
      {stop, normal, State};
  handle_info(_, State) ->
      {noreply, State}.
  
  