MARKER:  L = lua:function_machine( {marker_type="player_at", \
             func=(function(marker) crawl.mpr("Something ancient and \
             evil stirs ahead...", "warning") end) } )

MARKER:  L = lua:message_machine({marker_type="player_at", message="Something \
             ancient and evil stirs ahead...", channel="warning" })

--  marker_table: Table to be passed to the function when called. Defaults to {}.

-- The function will be called with the "marker" object as its only parameter.

-- The function will be called with the "marker" object and the table
-- marker_params.

  m.marker_params   = pars.marker_params    or {}

  self.func(marker)

  self.func(marker, self.marker_params)

  dgn.register_listener(dgn.dgn_event_type('entered_level'), marker)

  --dgn.register_listener(dgn.dgn_event_type('entered_level'), marker)

  lmark.marshall_table(th, self.marker_params)

  self.marker_params       = lmark.unmarshall_table(th)

function message_machine (pars)
  local channel = pars.channel or false
  local mtable = {message = pars.message, channel = pars.channel}
  pars.func = (function(marker, mtable) crawl.mpr(mtable.message, mtable.channel) end)
  pars.marker_params = mtable
  return FunctionMachine:new(pars)
end