Regarding MP3::Info, be careful if you plan on setting any tags, as you may not get what you expect. From the docs:

set_mp3tag (FILE, TITLE, ARTIST, ALBUM, YEAR, COMMENT, GENRE [, TRACKN
+UM])
set_mp3tag (FILE, $HASHREF)

    ID3v2 support may come eventually. Note that if you set a tag on a
+ file with ID3v2, the set tag will be for ID3v1[.1] only, and if you 
+call get_mp3tag on the file, it will show you the (unchanged) ID3v2 t
+ags, unless you specify ID3v1.
[download]

I'm assuming this is why the "manualtag" example is removing the ID3v2 tag.