I know thread::shared can't share deep data structure, so I attempt to only share the stringify memory address, and deref() it to access the structure inside the child thread. But what I got is really weird. Can someone help to explain how this happen? and any fix for this approach? Thank you very much 
$| = 1;
use threads;
use threads::shared;
use Devel::Pointer;
use Data::Dumper; $Data::Dumper::Sortkeys;

my $Addr :shared;
my $Deep = {OK=>1};
$Addr = address_of $Deep;

sub A {
    while ( 1 ) {
        my $Data = deref $Addr;
        $Data->{A}++;        
        print "Dumper in A tells:";
        print Dumper $Data;        
        print "B is now '$Data->{B}'"; # nothing!
        $Data->{B} = "Overide by A"; # The output suprised me!
        print $/; sleep 2;
    }
}

sub B {
    sleep 1;
    while ( 1 ) {
        my $Data = deref $Addr;
        $Data->{B}++;
        print "Dumper in B tells:";
        print Dumper $Data;
        print "A is now '$Data->{A}'";        
        print $/; sleep 2;
    }
}

my $A = threads -> create ( 'A' ) ;
my $B = threads -> create ( 'B' );
$A->detach; $B->detach;

while ( 1 ) { $Addr = address_of $Deep ; sleep 1 }

__END__
Surprising Output:
Dumper in A tells:$VAR1 = {
          'A' => 1,
          'OK' => 1
        };
B is now ''                      ## Nothing!
Dumper in B tells:$VAR1 = {
          'A' => 1,
          'B' => 1,  
          'B' => 'Overide by A', ## POSSIBLE?! Same key in Hash?!
          'OK' => 1
        };
A is now ''                      ## Nothing too!
Dumper in A tells:$VAR1 = {
          'A' => 2,
          'B' => 1,
          'B' => 'Overide by A',
          'OK' => 1
        };
...

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In reply to use Devel::Pointer in threads by exilepanda

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