#!/usr/bin/perl

use strict;
use warnings;
use utf8;
use Devel::Peek;
use Data::Dumper;
$Data::Dumper::Useqq = 1;

my $s;

{
 no utf8;
 $s = 'clé';
}

utf8::upgrade($s);

my %hash = (
    $s => 0,
);
my $key = (keys %hash)[0];
Dump($key);
print Dumper($key);

$hash{$s} = 1;
$key = (keys %hash)[0];

Dump($key);
print Dumper($key);

utf8::upgrade($key); # does nothing
Dump($key);
print Dumper($key);