#!/usr/bin/perl

use warnings;
use strict;
use threads;
use threads::shared;

my %hash :shared;

sub dumper {
  my $h = shift;
  my $ret = "{\n";
  while (my ($k,$v) = each %$h) {
    $ret.= "\t$k => $v\n";
  }
  $ret.= "}\n";
  return $ret;
}

sub sub1 {
  my $str = '[s'.threads->tid()."]\n";
  $str.= dumper \%hash;
  $str.= '[e'.threads->tid()."]\n";
  return $str;
}

$hash{a} = 1;
my $th1 = threads->new('sub1');
$hash{b} = 2;
my $th2 = threads->new('sub1');

my $a = $th1->join();
my $b = $th2->join();

print STDERR $a;
print STDERR $b;

##</code><code>##

[s1]
{
        a => 1
        b => 2
        a => 1
        b => 2
}
[e1]
[s2]
{
        a => 1
}
[e2]

##</code><code>##

[s1]
{
        a => 1
        b => 2
        b => 2
}
[e1]
[s2]
{
        a => 1
        a => 1
        b => 2
}
[e2]