-ok($res, 'uvar : cast succeeded');
-ok(check(), 'uvar : cast didn\'t triggered the callback');
+my $res = check { cast %h, $wiz } { }, 'cast';
+ok $res, 'uvar: cast succeeded';
+
+my $x;
+
+check { $x = $h{a} } { fetch => 1 }, 'fetch directly';
+is $x, 1, 'uvar: fetch directly correctly';
+
+check { $x = "$h{b}" } { fetch => 1 }, 'fetch by interpolation';
+is $x, 2, 'uvar: fetch by interpolation correctly';