"Perl holds truths to be self-evident." Unfortunately, PL/SQL does not. Perl's method of handling undef is simply ingenious. PL/SQL's method of treating NULL as "unknown and unknowable" is not. I can see I'm going to have a lot of problems with this concept.
I think on the SQL side it's going to make more sense. I still can't escape the feeling that something is not true unless you know it to be true.