#!/usr/bin/perl -l

BEGIN { $| = 1;}

use strict;
use warnings;
use utf8;
use Encode;
use CGI qw/:standard -utf8/;
use CGI::Carp qw/fatalsToBrowser set_message/;
$CGI::PARAM_UTF8 = 1;

BEGIN {
    sub handle_errors {
        my $msg = shift;
        print "<h1>There's a problem</h1>";
        print "<p>Cannot decode string: $msg</p>";
    }
    set_message(\&handle_errors);
}

my $q = CGI->new;
binmode STDOUT, ":encoding(UTF-8)";
my $referer_url = "@{[ $q->url ];}";
print $referer_url;
[download]

I get it, that strings shall not be double decoded. I got it to work without errors, but I do not get the UTF-8 displayed.

print $q->header(-charset => 'utf-8');
my $val = $q->param('key');
print utf8::is_utf8($val); exit;
[download]

This test gives me 1, which means, the value is UTF-8. But the value is not correctly displayed, just strange signs. Do you know what to do?

Thank you for this tip, I will use that to get better error messages. But yet it does not give me the string in UTF-8 and it shows the error again: The code is just as yours, with this in the end:

print $q->header;
print decode utf8 => $q->param('key');
[download]

The "decode utf8" is not needed in my opinion, as the input is already UTF-8, and same error "wide character" is shown on above. But without "decode utf8 =>" I get no errors, but I get this characters: �� -- occurrence is strange, as the script just worked fine with Unicode. Any clues?