ChangeLog: http://cpansearch.perl.org/src/RBUELS/Bio-GFF3-0.5/Changes
http://cpansearch.perl.org/src/RBUELS/Bio-GFF3-0.4/Changes
All they do is convert back and forth between low-level Perl data structures and GFF3 text. WWW: http://search.cpan.org/dist/Bio-GFF3/