If you stop off en route to Australia you will probably be jet-lagged in any event at your intermediate stop, as you are flying ahead in time, i.e. flying East. For example, Perth is 7 hours ahead of Dublin but so is Singapore. If you think you will be jet lagged on a flight to Perth you will also be if you stop off in Singapore. So fly direct to Australia and allow a day or so to get over jet lag. Then stop off somewhere, e.g. Bali and / or Singapore on the way back, as you are flying West.