Here I'll look at Kenny Perry's swing.
I would like to mention that Perry is indeed a great ballstriker and one of the very best over the last decade. In my PGA Tour total ballstriking stats, he usually finishes in the top 10 year after year. He's not even a great putter, but he hits it so well and is very long off the tee that he has a better chance of playing a par-72 as a par-68 than most golfers because not only does he have the distance to do it, but he's got the accuracy and consistency to keep him in play as well.
How long is he?
I paced him off at East Lake this year on a nice day and no wind and saw him drill a 4-iron on a pretty steep downward lie and drill it on the green with ease from 226 yards out.
Perry's swing IMO, reminds me a bit of Moe Norman's in that if you look at it in slow motion, you'll see that it's pretty orthodox and filled with a lot of quality mechanics. Check out these pics.
These positions really don't look all that unorthodox and I think most instructors would say that these are good positions here. He does straighten out his knees quite a bit here from where they were flexed at address. But from here he just makes a small peculiar move of reflexing his knees and turning the shoulders even more and making the 'across the line move.'
However, I believe that if I had to choose between having an across the line move or a laid off move, I would take the across the line move any day of the week because usually the across the line golfers have struggles with getting underplane. The laid off golfers tend to fight the dreaded over the top move.
That's one thing I didn't like about Hank Haney's analysis in the first episode of the 'Haney Project' with Ray Romano. An across the line move usually doesn't cause a golfer to come over the top. Thus I think Romano's issue is his wide open clubface at the top of the swing and because he has missed shots to the right, the subconscious tells him to come over the top so he can get the ball going more left. IMO, what he really needs to do is fix the clubface first and then get him out of habit of coming over the top.
But getting back to Perry...his swing isn't that unusual for the most part, just that one peculiar move. He also does keep his right foot down on the ground forever, an astute point made by Peter Kostis. Moe Norman did the same thing as well and I think when you keep it down for so long, while it's not flawed, it makes the swing look ugly, when it can be rather effective and dynamic.