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As David Richerby stated in his comment, you don't need a transit visa for Perth if you've already got a visa for Australia.
And according to Timatic, you don't need a visa for Hong Kong either if you stay in the transit area:
TWOV (Transit Without Visa):
Passengers with a confirmed onward (Air-to-Air or Air-to-Sea) ticket to a third country within 48 hours. They must stay in the international transit area and have documents required for the next destination.