"ODBC" is just a client-side interface; you still need a driver that implements it, and talks whatever wire protocol your database server can understand.

Assuming you're talking to DB2 on a z/OS host, you need something that will talk the DRDA wire protocol. There are no functional free drivers that do that, to my knowledge.

You probably want to buy DB2-Connect for whatever flavor of Unix/Linux you're using: http://www-306.ibm.com/software/data/db2/db2connect/

Then you can just install DBD::DB2 from CPAN, and connect with DBI->connect("dbi:DB2:55zosV8", "DAKPM", $pass)

PS: Good luck! You'll need it, since DB2 on z/OS is *freaking* *horrible*! :(