I'd probably go for Storable, unless your data has to be accessible in places other than perl.

If it does (need to be accessed by other languages), would I use XML? I'm not sure... I tend to focus on XML (the syntax) being either a long-term storage format, or a transport format. Or I use XML (the data format) as an intermediary system for giving me access to great tools (e.g. using XML::Generator::DBI so I can use XML tools with databases).

So if you don't know XML, and want some form of cross-platform short-term storage format, I'd use a database. It'll be faster and easier to use for you.

But if you don't need all that cross platform gubbins, and the cool tools XML gives you don't grab you, then use Storable. It rocks, and it just plain works.

(And yeah, this is from a guy who lives and breathes XML)