I dunno if this is what you mean by a !listall command. But I like it.

  if ($1 == !listall) {
    if ($2 == stop) { play stop }
    else { play $chan learnt.txt }

Will have the bot read back the learnt.txt file to the channel
typing !listall stop

stops it.

We don't just write the scripts, we put them to the test! (ScriptBusters)