The DBI module enables your Perl applications to access multiple database types transparently. You can connect to MySQL, MSSQL, Oracle, Informix, Sybase, ODBC, and other database systems without having to know the different underlying interfaces of each. The API defined by DBI will work on all these database types and many more. You can connect to multiple databases of different types at the same time and easily move data between them.
The DBIWrapper is a Perl Module that provides for easier access to databases using DBI. It supports MySQL, PostgreSQL, and ODBC DBD modules. High level methods for reading, writing, commiting, and rolling back transactions to the database are provided. XML or DBI data structures can be used.
DBIx-Class is an SQL to OO mapper with an object API inspired by Class::DBI (with a compatibility layer as a springboard for porting) and a resultset API that allows abstract encapsulation of database operations. It aims to make representing queries in your code as Perl-ish as possible while still providing access to as many of the capabilities of the database as possible, including retrieving related records from multiple tables in a single query.
DBIx::AnyDBD is a Perl module for developers writing cross database applications. It allows you to write "plugins" for different DBD drivers (Oracle, Sybase, etc) so that your application can do different things on different databases. It doesn't provide any compatibility layer - just an intelligent method to switch to the right class to use at runtime.