Case 1: non existent
$VAR1 = {
          'y' => {}
        };
Case 2: undef
$VAR1 = {
          'y' => {}
        };
Case 3: hashref
$VAR1 = {
          'y' => {}
        };
Case 4: stopper scalar
$VAR1 = 'stopper';
Case 5: Even assignment won't do, and won't trigger warning or runtime error!
$VAR1 = 'stop2';
Case 6: use strict is your friend :)
Can't use string ("stop3") as a HASH ref while "strict refs" in use at ./autoviv-stop.pl line 35.