hello perth

An Australian expression used to convey that the information is old news and has been heard or seen before. This stems from the timezone of Perth, Australia being 2-3 hours behind the rest of Australia, with Western Australian residents often being the last to hear about anything.

More recently used in group messages, to indicate the same meme has already been sent to the group.

Alan: Did you hear Jake joined the army?
Charlie: Hello Perth!