Bug 9239 follow-up: POD and perlcritic fixes

Bug 9239 follow-up: POD and perlcritic fixes

There were several perlcritic violations for returning explicit undef,
and splitting up the various driver classes resulted in POD compliance
errors, where the POD was starting with head2 rather than head1. This
patch fixes those errors (but has no functional impact).

Signed-off-by: Elliott Davis <elliott@bywatersolions.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>