my $fork_pid = fork();

if ($fork_pid == 0)									#If its the child process
{
   write_pid();
   exit(0);
}
elsif ($fork_pid)									#If its the parent process
{
   wait();

   if ($limit_file_size == 1)
   {
      checkFilesize();
   }

   untaintInput();
   uploadFile();
   output();
   dump_pid();
}
else
{
   die "Couldn't fork.";	
}

sub uploadFile 
{
   my $upload_filehandle = $query->upload($form_input_name);			#grab handle of temporary file

   open ( UPLOADFILE, ">$upload_dir/$filename" ) or die "$!";			#open file for write or report errors
   binmode UPLOADFILE;								#write the file in binary mode

   while ( <$upload_filehandle>)
   {
     print UPLOADFILE;								#write actual file from the temporary file
   }

   close UPLOADFILE;
}

sub output
{
   #Output page
   print $query->header();
   print "{success: true, data: 'Your file was uploaded successfully!'}";
}

sub write_pid 
{
   open(MYID, ">" . $upload_dir . '/' . 'current_upload_pid.txt'); 
    print MYID $$;
    close(MYID); 
}