Ronaldo left Real Madrid for Juve in a €112m deal.
“The news really struck me, he's the best in the world," Perin said at his presentation Press conference.
“It means I can train with someone who has such great professionalism, even though there are many here, starting with [Giorgio] Chiellini and [Andrea] Barzagli.
“To learn from him will be a positive for us, for the players and also for Serie A which will be among the two or three best leagues in the world.
“Was I surprised? I wasn't expecting it, but rom a club like this it doesn't surprise me to sign such a great champion.
“We know that a great champion is coming and we're happy." Perin was also quizzed about his own move to Turin.
“I went through a long and tortuous path to join a great team. I'm at one of the top four or five teams in Europe, which is what I worked for, but I don't feel like I've arrived.
“Everyone thought I'd have chosen the easiest way but I like a challenge and I come here with the willingness to learn. The competition will be good for both myself and [Wojciech] Szczesny.
“I know that I'll start disadvantaged but the competition will be good for both of us. Szczesny played some great games and he deserves the chance to replace Gigi [Buffon].
“I'll work and give my best when I play, then beyond that the decisions aren't down to me.
“I spoke with three or four clubs but I think I made the best choice because the chance to go to Juventus only comes along once in a lifetime. I didn't think twice about it."