As you can see from these test results:
matrix.cpantesters.org/?dist=Text-Una...
this has had an unpatched bug report for ten years or so where it doesn't cope with sixty-four bit systems:
rt.cpan.org/Public/Bug/Display.html?i...
It's regrettable that people are using this as a dependence even now:
metacpan.org/requires/module/Text::Un...
Another thing worth noting is that this module completely ignores Perl's Unicode encoding. Try commenting out the "use utf8;" in the following:
use utf8;
use Text::Unaccent;
my $charset = 'UTF-8';
my $string = 'ÀÁÂÃÄÅAあ';
print unac_string($charset, $string);
The output results will be identical.