Class::DBI provides a convenient abstraction layer to a database.

It not only provides a simple database to object mapping layer, but can be used to implement several higher order database functions (triggers, referential integrity, cascading delete etc.), at the application level, rather than at the database.

This is particularly useful when using a database which doesn't support these (such as MySQL), or when you would like your code to be portable across multiple databases which might implement these things in different ways.

In short, Class::DBI aims to make it simple to introduce 'best practice' when dealing with data stored in a relational database.