Unicode uses two bytes per character

For characters like ř, it's true, but for Chinese, it's not. UTF-8 is a "variable-length" encoding.

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use open ':encoding(UTF-8)', ':std';

use Encode;

chomp( my $chinese = <> );
say length $chinese;

my $octets = encode('UTF-8' => $chinese);
say length $octets;
[download]

Where the input contains (UTF-8 encoded):

焚书坑儒

Output:

4
12
[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]