Perry played in the NFL for seven seasons with the Pittsburgh Steelers before becoming their secondary coach for four seasons. He has spent the last two seasons as the Packers safeties coach.
If you're an astute observer, something should be hitting you right now. Perry, while he might be a good coach, has played and coached in 3-4 for his entire career. Head coach Andy Reid has said the Eagles will continue to run the 4-3, so why would a guy with only a 3-4 background even be a candidate?
Sean McDermott was bad, but what do they really expect from a guy who has never run the 4-3? Instead of Perry, why not talk to a guy like Mike Trgovac who has run a 4-3 defense successfully in the past?
Perry's not as young as McDermott was, but he's only 42. And since he has no experience with a 4-3, the little bit of age he has on McDermott really doesn't mean a thing.
If they really want Perry, try to pass off a job as the secondary coach as a promotion. Right now, Perry only coaches the safeties in Green Bay, so technically it would be a promotion, it would all depend on what Packers head coach Mike McCarthy thinks of the move and whether he feels it's enough of a promotion to let Perry walk.
Of course, Perry would also want to accept the job, but it's probably unlikely he turns down an opportunity to coach the entire secondary rather than just half of it.
As a secondary coach, Perry would be a good option -- since he's helped groom a guy like Nnamdi Asomugha and now Nick Collins and Morgan Burnett. But as a defensive coordinator, this sounds like a disaster in the making. There are key differences between the 3-4 and the 4-3, and it would probably take Perry a couple years to get down the nuances of the switch.
If they were going to go out and get a guy who would need a couple years to really hit his stride, why wouldn't they have just kept McDermott instead?