my $n = 0 ;
  my $s = $p ;
  my $l ;
  do {
    if ($l = unpack("\@$p C", $response)) { $n++ ; } ;
    $p += $l + 1 ;
  } while ($l) ;

##</code><code>##

  my ( ...., @labels, undef, $type, $class, ...) = unpack(".... (C/a*)$n C n n ....") ;

##</code><code>##

  ($name, $p) = extract_name($response, $p) ;
  ....
  sub extract_name {
    my ($response, $p) = @_ ;
    my $extracted ...
    ....
    return ($extracted, $p) ;
  } ;

##</code><code>##

  sub extract_name {
    my ($response, $p) = @_ ;
    my $extracted ...
    ....
    $_[1] = $p ;         # $_[1] is implicitly a reference to the 2nd actual argument
    return $extracted ;
  } ;