function register_persitent_tag(name, reader, writer)
	old_on_load = wesnoth.game_events.on_load
	old_on_save = wesnoth.game_events.on_save
	function wesnoth.game_events.on_load(cfg)
		for i = 1, #cfg
			if cfg[i][1] == name then
				reader(cfg[i][2])
			end
		end
		old_on_load(cfg)
	end
	function wesnoth.game_events.on_save(cfg)
		local res = old_on_save()
		table.insert(res, { name, writer()})
		return res
	end
end