Dan Pemstein the author of Ogg::Vorbis::Header was aware of the problem with requiring rather than using his module (apparently it's an issue with Inline) and (even better) he knew a workaround for it.
So I've now released AudioFile::Info::Vorbis::Header. There are now four plugins available for AudioFile::Info, two that are pure Perl (AudioFile::Info::Ogg::Vorbis::Header::PurePerl and AudioFile::Info::MP3::Info and two that use external libraries (AudioFile::Info::Ogg::Vorbis::Header and AudioFile::Info::MP3::ID3Lib). I think that's enough to cover most requirements so I'll stop there for a while.
My next plan (and the real reason that I started on this) is to write something to replace Apache::MP3 which uses AudioFile::Info and the Template Toolkit.