while ( ($key, $value) = each %hash ) {
  print "$key => $value\n";
}
##</code><code>##

use 5.010;

say '[', scalar (3..4), ']';
say '[', scalar (undef, undef), ']';
say '[', scalar (undef, 1, undef, 5), ']';

@a = (3..4);
@b = (undef, undef);
@c = (undef, 1, undef, 5);

say '[', scalar @a, ']';
say '[', scalar @b, ']';
say '[', scalar @c, ']';

say '[', scalar 3..4, ']';
##</code><code>##

[]
[]
[5]
[2]
[2]
[4]
[34]