in reply to Difficulty with UTF-8 and file contents

I'm going to take a guess that, because unfortunately PerlMonks' <code> tags do HTML-escaping of Unicode characters, what you pasted in the HTML is actually ‘Def’, which shows that you appear to already have encoding issues somewhere - the original string is probably ‘Def’.

k-mx already pointed out that the DATA filehandle doesn't need to be opened, and the use utf8; already causes the source code, including the __DATA__ section, to be read as UTF-8 (Special Literals). The following works fine for me, that is, the source file and the output are both UTF-8 (and I've made sure to accommodate for PerlMonks' Unicode oddities):

#!/usr/bin/env perl
use warnings;
use strict;
use utf8;
use open qw/:std :utf8/;
use HTML::TreeBuilder::XPath;

my $xhtml = HTML::TreeBuilder::XPath->new;
$xhtml->implicit_tags(1);
$xhtml->no_space_compacting(1);
$xhtml->parse_file(*DATA) or die $!;
print $xhtml->as_XML_indented;

__DATA__

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>Foo</title>
  </head>
  <body>
    <p><a href="https://example.com/3/">Abc
      ‘Def’ (GHI)</a></p>
  </body>
</html>

Note that I added the use open qw/:std :utf8/; because the script is also printing Unicode strings. So basically, I think that you need to inspect your source file's encoding (my script enctool might be helpful).

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