I ran into this just the other day. &DBI::connect returns a blessed reference to a DBI::db object, not a DBI oject:

$ perl -MDBI -e '$db = DBI->connect("DBI:mysql:database=test;user=x", 
+"x", "x"); print "\$db is a ", ref $db, "\n"'
$db is a DBI::db
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I just settle for a 'has-a' relationship (my object "has a" DBI thingy in it) and leave it at that, works fine. Oh, it might be a good idead to invoke the disconnect method in your DESTROY sub so you won't get those nasty little warnings when the object goes away.