Considering the rather depressing situation with Perl modules handling ogg-vorbis, this is one of the better modules in that it at least works.
However, its documentation is in parts inaccurate or even wrong. In order to understand how to retrieve the tags, I eventually had to look into the module's test-script. It turns out that Ogg::Vorbis::Header::comment() doesn't return a list of values (as advertized by the documentation) but rather an array which makes quite a difference in scalar context.
As for the test-script, it contains some rather questionable constructs. Also, it's not portable.