[PD] Store some lists with undo function?

[JF]

I'm experimenting with a message sequencer that will play back time tagged lists.

So far I've looked at [qlist] [textfile] and rjlib's [u_cocollect].

Are there any relatively simple approaches to 'undo'-ing the last list written to any of these 

objects?

I'm a little stumped on it to be honest other than complicated writing to buffers and 

attempting to prune the last list somehow.


Thanks,
John.