ExifTool use UTF-8 as default. If I print it out w/o encoding, the text is correct with charset set to UTF-8. So the decoding is done, or the source is UTF-8.
Comment on Re^2: How to encode for non-unicode output
If the source is UTF-8, most string operations (like encoding into a specified character encoding) behaves very differently in the two cases (decoded or not decoded).
If it's indeed decoded, encode($destination_encoding, $string) will work (but you still need to know in which encoding you want to store it).