use strict;
use warnings;

use MCE::Mutex;
use MCE::Shared;

my $mutex = MCE::Mutex->new();
tie my $cntr, 'MCE::Shared', 0;
my $val;

if ( ! defined ( my $pid = fork() ) ) {
   die "Cannot fork!: $!";
}
elsif ( $pid == 0 ) {
   # Child
   for ( 1 .. 10000 ) {
      $mutex->lock;
      $val = $cntr++;
      $mutex->unlock;
   }
}
else {
   # Parent
   for ( 1 .. 10000 ) {
      $mutex->lock;
      $val = $cntr++;
      $mutex->unlock;
   }

   waitpid( $pid, 0 );

   print "counter: ", $cntr, "\n";
}