Why not work POSIX::RT:Semaphore

From: Dima (_asr__at_inbox.ru)
Date: 03/24/05 

Date: 24 Mar 2005 05:45:44 -0800

This is my simple code

#!/usr/local/bin/perl
use threads;
use threads::shared;
use POSIX::RT::Semaphore;

$sem = POSIX::RT::Semaphore->init(0, 0);

my $pid = fork;
if ( $pid == 0 )
  {
    $sem->wait;
    print "CODE2\n";
    exit;
  }

print "CODE1\n";
$sem->post;

Why I see only CODE1???
Why after post in parent process semaphore value in child process was't changed?