FYI: # $chinese = "籝籱籮 籫籾籽籵籮类 籭籲籭 籲籽簪"

use strict;
use warnings;
use utf8;
use open ":std", ":encoding(UTF-8)";
use Test::More;

# rot8000 v1.005;

my %rot;
init_rot();

my $english = "The butler did it!";
my $chinese = "籝籱籮 籫籾籽&#3186
+1;籮类 籭籲籭 籲籽簪"
+;

# fix PerlMonks' Uni<code>Mess
$chinese =~ s/&#(\d+);/chr($1)/ge;

is(
   rot8000($chinese),
   $english,
   "chin2engl -> $english"
  );

is(
   rot8000($english),
   $chinese,
   "engl2chin -> $chinese"
  );

my $random = join "", map { chr int rand 2**16-1 } 1..30;

is(
   rot8000(rot8000($random)),
   $random,
   "Identity"
  );

done_testing;



sub rot8000 {
    my ($in) = @_;
    my $out;
    for my $char (split //,$in) {
        $out .= $rot{$char} // $char;
    }
    return $out;
}


sub init_rot{
    my @toggles = reverse (0, 33,127,161,5760,5761,8192,8203,8232,8234
+,8239,8240,8287,8288,12288,12289,55296,57344);

    my @allowed = map chr, 0.. 2**16-1;


    while ( my ($stop,$start) = splice @toggles, 0, 2 ) {
        #say "$start-$stop";
        splice @allowed, $start, $stop-$start;
    }

    my @allowed_low = splice @allowed, 0, (@allowed/2);

    @rot{@allowed_low} = @allowed;
    @rot{@allowed}     = @allowed_low;
}
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