In British informal English, if you say you are perished, you mean you are extremely cold — so cold it almost hurts. People say it about themselves after standing outside: “I’m perished.” It is spoken British, a little old-fashioned in some places, and not the usual word in American English. Though actually, the same spelling is also the past of perish, meaning died or was destroyed (“the plants perished in the frost”). This sense is only the cold feeling. It probably grew from the idea of being so cold you might not last, but in real talk it is just a strong way to say “freezing”.