Shutter Island Revisited

Someone who is more steeped in film history than me has pointed out that most of Shutter Island is in fact a homage - and that's pronounced homidge, not homarge, just so we're clear - to Hitchcock. Scene after scene references (did I really just use that word as a verb? Shame on me,) the master's work.
Which is great. The only problem, of course, is: you have to know to know.