gistfile1.txt

$] = 5.008008
$URI::VERSION = 1.71
https://www.example.com?hoge=%E3%81%BB%E3%81%92
https://www.example.com?hoge=%C3%A3%C2%81%C2%BB%C3%A3%C2%81%C2%92&foo=bar

test.pl

use strict;
use warnings;
use URI;
use URI::QueryParam;

print "\$] = $]\n";
print "\$URI::VERSION = $URI::VERSION\n";

my $u = URI->new('https://www.example.com');
$u->query_param(hoge => 'ほげ');
print "$u\n";

use utf8;
$u->query_param(foo => 'bar');

print "$u\n";