or download this
c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my %args = ('profile' => 'foo', 'xyzzy' => undef, 'status' => 0);
...
("filtered", { profile => "foo", status => 0 })
("original", { profile => "foo", status => 0, xyzzy => undef })