sub process_all_errors
{
  my ( $twig, $errors_list ) = @_;
  foreach my $error ( $errors_list -> children ( "error" ) )
  {
    print "NEW: ",$error -> first_child_text('desc'),"\n"; 
  }
}

my $other_parser = XML::Twig -> new ( 'twig_handlers' => { 'errors' => \&process_all_errors } );
$other_parser -> parse ( $XML );