use strict ;
use warnings;
use Thread;
use threads::shared;
use Carp qw (cluck) ;
my %all_shary_for_subs           :shared;
my %sim_info                     :shared;     

$all_shary_for_subs{'%sim_info'}=\%sim_info;

cluck("the sim_info glob ref is:" . \%sim_info . "\n" );
cluck("And in the hash it is:" . $all_shary_for_subs{'%sim_info'} . "\
+n"  );
[download]

use strict ;
use warnings;
use threads;
use threads::shared;
use Data::Dumper;
my %HoH           :shared;
my %hash          :shared;     

$hash{pre_key} = "Before";
$HoH{hash}=\%hash;
$hash{post_key} = "After";

if (\%hash eq $HoH{hash}) {
   print "OK\n";
} else {
   print "Copied, I suspect\n";
}

print Data::Dumper->Dump ([\%hash], ["hash"]);
print Data::Dumper->Dump ([$HoH{hash}], ["HoH"]);

print "But looks like they still stay in sych\n
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Output

Copied, I suspect
$hash = {
          'pre_key' => 'Before',
          'post_key' => 'After'
        };
$HoH = {
         'pre_key' => 'Before',
         'post_key' => 'After'
       };
But looks like they still stay in sych
[download]

Update

I just read the docco for threads::shared and found this gem, which explains your issue:

Using refaddr()) is unreliable for testing whether or not two shared references are equivalent (e.g., when testing for circular references). Use is_shared(), instead:

There is more detail, and an example of the correct way to test in said docco

Cheers,
R.

Pereant, qui ante nos nostra dixerunt!

the Thread module is deprecated. Go for threads. Having said that I can add use threads; just fine, but I am seeing the mis-match whenever I use threads::shared;. It looks like threads::shared is making a copy of the hash

Cheers,
R.

Pereant, qui ante nos nostra dixerunt!