use strict;
use warnings;

use XML::Twig;

my $xml = do { local $/; <DATA>; };

#my $conv = XML::Twig::encode_convert( 'latin1'); # failed
my $conv = 'latin1'; # failed

my $twig = XML::Twig->new( input_filter => $conv );
$twig->parse( $xml );

__DATA__
<?xml version = '1.0' encoding = 'UTF-8'?>
<Text>5CH (the BACKSLASH ý\ý in ISO-IR 6) shall</Text>