My recommendation: use a real SQL database if it's available. You'll need to write some administration scripts for easy manipulating the database, but that's not too hard (Maybe only submitting raw SQL Queries to the database).

Working with databases is extremely easy with Perl, thanks to the DBI. The DBI manpage is at least a good tutorial on the module only. I've read "Programming the Perl DBI", so I'm unable to give you other ressources, for i've never needed any apart from the book and the manpage...

Some more Pros for mySQL:

• fast
• extensible
• Learning SQL is good and you're likely to need it sometime, so learn it now...
• DBI is a powerfull tool. Learn to know it now and you'll be able to use it in future projects.
• The time you spend now learning the stuff will be spared as soon as you need the features a flat BerkeleyDB can't give you.