anchor.diff:  update_queue_in_list_of_queues(Key, Q, Queues) ->
       case queue:is_empty(Q) of
           true ->
  -            lists:keydelete(Key, 1, Queues);
  +            erlang:erase(Key),
  +            lists:delete(Key, Queues);
           false ->
  -            Tuple = {Key, Q},
  -            lists:keyreplace(Key, 1, Queues, Tuple)
  +            _ = erlang:put(Key, Q),
  +            Queues
       end.
  
positive.code:                                  Possibilities::pos_integer(),
                                   state_t()}.
  pop_random_message(#state{msg_queues = OldQueues} = State) ->
      {{{Src, Dest} = Key, Q}, Len} = util:randomelem_and_length(OldQueues),
      {{value, {LorG, M}}, Q2} = queue:out(Q),
      NewQueues = update_queue_in_list_of_queues(Key, Q2, OldQueues),
      State2 = State#state{msg_queues = NewQueues},
  
negative.code: 
  -type queue_key()        :: {Src :: comm:mypid(), Dest :: comm:mypid()}.
  -type delay_queue_key()  :: {Dest :: comm:mypid()}.
  -type msg_queues()       :: [queue_key()].
  -type msg_delay_queues() :: [delay_queue_key()].
  
  -record(state,
          {msg_queues              = ?required(state, msg_queues)
  