I've been trying something like this too, but I didn't get the map working (I tried to use a 'values %hash' loop instead of your 'getkey' function, but there I had the same problem of pseudo-random order). I have to remember the shift rotating trick, though...

Breakage is not an issue, since I make (lock/edit/...) the files myself and can therefore guarantee their integrity. Or so I hope. ;)