use strict;
use warnings;
use Data::Dumper;
use Digest::MD5 qw/md5_hex/;
use Storable;
use POSIX qw/mkfifo/;

my $fifo = int(rand(999999999));
mkfifo($fifo, 0600) or die $!; 

my $md5 = Digest::MD5->new();
my $string = 'Hello World!';

if (fork) {
   my $freezed_data = Storable::nfreeze(\$string);
   my $md5_hex_sum  = md5_hex($freezed_data);
   my $data_packet  = pack("N/a*", $freezed_data);
   open my $fh, '>>', $fifo or die $!; 
   print $fh $md5_hex_sum, $data_packet or die $!; 
   close $fh;
   exit;
}

open my $fh, '<', $fifo or die $!; 
32 == read($fh, my $md5_buf_sum, 32) or die;
4 == read($fh, my $buffer, 4) or die;
my $length = unpack("N", $buffer);
$length == read($fh, my $freezed_data, $length) or die;
close $fh or die;
unlink($fifo) or die;
my $md5_hex_sum = md5_hex($freezed_data);
$md5_buf_sum eq $md5_hex_sum or die;
print "MD5 $md5_buf_sum\n";
print "MD5 $md5_hex_sum\n";
my $ref = Storable::thaw($freezed_data);
print Dumper($ref);