You are in fact using the DBI module. The DB handle is probably (I think it is) a bless reference that will send you straight to the DBI module that's called in the function you've created. Although you're not using the DBI module in your code, you're indirectly using it without ever knowing it if you made a good enough class.
I think. I hope. Maybe I'm completely wrong. I don't know. Someone will correct me though. Right or Wrong. Will