DBI dropped compatibility with Perl's earlier than 5.6.0 at about 1.37 - currently they support 5.6+ with every release, until they advise otherwise.

I know this because we still have some old Solaris boxes with the default Perl 5.005 installed, and we have to use DBI 1.37 with those, later versions moan vociferously about an 'ancient perl'.