The Perl 5 module XML::FeedPP is an all-purpose syndication utility
that parses and publishes RSS 2.0, RSS 1.0 (RDF), Atom 0.3 and 1.0
feeds. It allows you to add new content, merge feeds, and convert
among these various formats. It is a pure Perl implementation and
does not require any other module except for XML::TreePP.