Wanna modify MP3 tags ?
"Every self-respecting computer and music fan needs to be able to manipulate MP3s -- the defacto standard for recreational digital music use. In this article, Ted looks at ways to manage and manipulate MP3s (searching, tagging, renaming, commenting, etc.) using the autotag.pl application. Ted takes you through the application, illustrating how CPAN modules enable the application." -> MP3 files could be tagged with ID3 tags. Inside the file was information about it -- what's commonly known as metadata.