Encode::Guess is likely to be helpful for figuring out the source encodings for many of the Asian (multi-byte-char) strings, though it might not help much for distinguishing among single-byte encodings. Worth a try.
I've been using Encode::Guess, but have had trouble building a suspects list for some data. However, Firefox hasn't been able to appropriately handle the problem data, either, so if Encode::Detect is the same method, I doubt it would've done any better on this data.