my %hash = (
  foo => 1,     bar => 1,      baz   => 1,
  one => undef, two =>  undef, three => undef,
);

print "defined     - ", scalar(grep  defined, values %hash), $/;
print "not defined - ", scalar(grep !defined, values %hash), $/;

__output__

defined     - 3
not defined - 3