This isn't really a Perl question. If, and what kind of database you need, depends on the problem you want to solve, and it's a largely language independent problem. If for instance I need to program a flight reserve system, I get lots of records that need to be stored, retrieved quickly, summaries need to be made, and it needs to be backupped and be able to restored quickly. Then you need a relational database (and a good one, not MySQL). If I just have some key/value pairs that I want to remember from one invocation of the program to another, one of the DBM files will do. If I have some mostly static data, and I'm going to need most of the data each time the program is run, a flat file will do fine.

So the answer is "it depends on your data". What structure does it have, is it volatile, how do you want to search it, how important is it, what's your backup solution, etc, etc. Answer all these question, and then you can start looking what database you need.

Abigail