I'm not sure how vague to make my answer, but Template-Toolkit comes with a plugin for XML::RSS, it's straightforward to "call code from a separate file" (see Simple Module Tutorial or Including files or even Writing Modules for CPAN), and there's different ways to store your SQL in another file (e.g. database abstraction layers like Class::DBI or DBIx::Class...also see A brief survey of the DBI usability layer modules on the CPAN, or straight SQL storage like SQL::Catalog).