#!/usr/bin/perl -w
use strict;
#this code is for WinXP, not Unix

$| =1;          #buffering is off!

print "my Parent ID at start is: $$\n";

my $pid = fork();

if (!defined($pid))
{
   die "Couldn't fork"; 
}

if ($pid == 0) #I am a child ##
{
     print "My child PID =$$\n"; 
     my $c =0;
     while ($c<10)
     {
       print $c++;
       sleep(1);
     }
     print "\n";
}

else         # I am parent ##
{
     print "Parent PID  = $$\n";     
}
print "end of PID  = $$ process ID\n";	

__END__
PRINTS:
my Parent ID at start is: 3640
Parent PID  = 3640
end of PID  = 3640 process ID
My child PID =-1628
0123456789  (one digit per second)
end of PID  = -1628 process ID