sub do_stuff {

          +-----+  +------------------+
$href --->| a: --->| status: "OK"     |
          +-----+  +------------------+


    my $hash = dclone(shift);

          +-----+  +------------------+
$href --->| a: --->| status: "OK"     |
          +-----+  +------------------+

          +-----+  +------------------+
$hash --->| a: --->| status: "OK"     |
          +-----+  +------------------+


    $hash->{'a'}->{'status'} = "NOT OK";

          +-----+  +------------------+
$href --->| a: --->| status: "OK"     |
          +-----+  +------------------+

          +-----+  +------------------+
$hash --->| a: --->| status: "NOT OK" |
          +-----+  +------------------+


    print "IN SUB: " . $hash->{'a'}->{'status'} . "\n";
    return 0;
}