This is one part (of many) of perl that I like, that it exposes the pointer-y parts to the programmer (to abuse :))

    # hash
    my %a = ( 'one' => 1, 'two' => 2 );
    my %b = %a;

    $b{ 'two' } = 99;

    # prints 2
    print $a{ 'two' }, "\n";

    # reference to hash
    my $a = { 'one' => 1, 'two' => 2 };
    my $b = $a;

    $b->{ 'two' } = 99;

    # prints 99
    print $a->{ 'two' }, "\n";