I personally would look at something like the before mentioned MySQL, however as an alternative you could consider sticking your data in a hash, then store it using storable. Using storable you can suck in your hash (actually, your arbitrary data structure) use it, then throw it back at the disk. Nice and easy, and certainly free.

Personally, I would go for a normalised RDBMS.

If you go for a well known RDBMS, you get the benifit of the experience of 1000's of users, admins and have heaps of resources out there on the web to help you.

You would normalise the database in order to provide for future expansion, maintainability, scalability, and performance.

Other possible alternatives are CSV files and DBI::CSV or SQLite which is a self contained RDBMS.

Sounds like a nice project to get your teeth into.. good luck.