oalders/http-browserdetect — comment on commit 793d06a06c0a03613351c6b7159ab568acae78d4
File:  line 0
By obilodeau:

@tamias, returning an explicit undef is not a recommended thing to do in perl:
http://search.cpan.org/dist/Perl-Critic/lib/Perl/Critic/Policy/Subroutines/ProhibitExplicitReturnUndef.pm

What problem are you trying to solve here? Maybe I don't understand without the context.