Where to start..? It is a nuisance and fantastic (No I don't have it, but I know lots of people who live and work with it)
Best go here, loads of "beginners" questions ;-)
https://www.quora.com/search?q=perfect+pitch
As it is, with age, your perfect pitch tends to change, extremely unrattling, and the above post does not really take into account the difference between pitch and intonation - the guy might have very well noticed, how it turned sour, well trained ears have this ability, but then you all know the terrible choirs going downhill thinking they are completely in tune. or great soloist singers who cannot hear there intonation because of the head pressure, thats basically training, otherwise THEY tend to rise..
and so on. Intonation is a miracle.