[PATCH] Clear up perlcritic 'missing return' warning

This is the first in a series of patches to reduce the number of warnings
from perlcritic. The current plan is to submit a separate patch for each
warning or small set of related warnings, to make reviewing more
straightforward.

This particular patch addresses the warning caused by falling off the end
of a subroutine rather than explicitly returning. It also contains
additions to the perlcritic configuration file to ignore a couple of
warnings that seem acceptable, bringing it in line with the buildfarm's
configuration for those warnings.

Thanks to Andrew for assistance getting my environment set up.

Mike Blackwell