anchor.diff:      SerialPort = serial:start(Options),          
       fun F(_N, Meta) ->
           {F, {serial,
  -            fun (Data) -> SerialPort ! {send, Data} end
  +            fun (Data) -> SerialPort ! {send, Data}, ok end,
  +            fun () -> ok end
           }, [{output, serial} | Meta]}
       end.
   
  
positive.code: 
  %% last member find
  -spec last_output(any()) -> any().
  last_output(L) when is_list(L) -> last_output(lists:last(L));
  last_output(F) when is_function(F) -> last_output(F());
  last_output(X) -> X.
  
  
negative.code: write_really(Data, {https, _Final}) -> {ok, Data};
  write_really(Data, {net, Writer, _Closer}) -> {Writer(Data), <<>>};
  write_really(Data, {exec, Writer, _Closer}) -> {Writer(Data), <<>>};
  write_really(Data, {serial, Writer, _Closer}) -> {Writer(Data), <<>>};
  write_really(Data, Fd) -> {file:write(Fd, Data), <<>>}.
  