my $t = XML::Twig->new(
    twig_roots => {'nitf/body/body.head/hedline/hl1' => \&fix_hl1,
                   'nitf/body/body.head/hedline/hl2' => \&fix_hl2,
                    _default_ => \&fixup,
                  },
        twig_print_outside_roots => 1,
        keep_encoding => 1,
);

##</code><code>##

sub fixup {
    my ($tree, $elem) = @_;

    my $tag = $elem->tag;
    plog("in fixup:  tag = $tag");

    if ($fixup_tag{$tag}) {
        my $t = $elem->text;
        conv_chars(\$t);
        $elem->set_text($t);
    }

    $elem->print;
}