use Data::Dumper;

$h{a} = [qw/x y z/];
$h{b} = &{sub {\@_}}(@{$h{a}});

$h{a}->[0] = 'new_x_is_shared';
push @{$h{a}}, 'pusher_is_not_shared';

print Dumper $h{a};
print Dumper $h{b};
[download]

with the output:

$VAR1 = [
          'new_x_is_shared',
          'y',
          'z',
          'pusher_is_not_shared'
        ];
$VAR1 = [
          'new_x_is_shared',
          'y',
          'z'
        ];
[download]