I've been stumped with a bug in my code for days, until I traced it down to a fairly simple subroutine that gave inconsistent results when two or more threads were running. Here's an isolated version of the problem: 
#!/usr/bin/perl
use strict;
use warnings;
$|=1;

use threads;
use threads::shared;

my %testOne :shared = (A => 1, B => 2, C => 3, D => 4, E => 5);
my %testTwo         = (A => 1, B => 2, C => 3, D => 4, E => 5);
my $inc :shared = 1;

do {
    threads->create(sub {
        while (1){
            my $i = join('', sort keys %testOne);
            my $j = join('', sort keys %testTwo);
            print "$inc-1\t$i\n" if ($i ne 'ABCDE');
            print "$inc-2\t\t$j\n" if ($j ne 'ABCDE');
        }
    });
} while (sleep 5 && $inc++ && $inc < 100);

[download]
I'm running this with Strawberry Perl on Windows, and my application uses threads so the Tk GUI doesn't freeze. I want to be able to use a lot of worker threads for a CPU-bound genetic sorting algorithm. Is this a bug in perl, or have I misunderstood something?

In reply to Inconsistent results with keys on thread shared hashes by izomiac

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