my $t = XML::Twig->new(
        twig_roots => { "$nitf_root/body/body.head/hedline/hl1" => \&fix_hl1,
                        "$nitf_root/body/body.head/hedline/hl2" => \&fix_hl2,
                      },
        twig_print_outside_roots => 1,
        keep_encoding => 1,
);