grep: 1 ... 2
test: no

FAIL! h{x} modified, h{y} not modified... why?

$VAR1 = {
          'a' => 1,
          'b' => '',
          'c' => 2
        };

$VAR1 = {
          'a' => 1,
          'b' => '',
          'c' => 2,
          'x' => undef
        };