use strict;
use warnings;

use IPC::Shareable;

my $options = {
   create    => 1,
   exclusive => 0,
   mode      => 0644,
   destroy   => 1,
};

tie my $cntr, 'IPC::Shareable', $options;
my $val;

$cntr = 0;

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

   waitpid $pid, 0;

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