my $url = $cgi->param('url');
my $file = url2file($file);
my $fh = FileHandle->new("< $file");
if ($fh)
{
  # Executable means it's a partial download
  if (-x F)
  {
    # If it's not locked, the download process has died
    if (flock(F, LOCK_EX|LOCK_NB))
    {
      $fh=get($file,$url)
        or die "Couldn't get URL!\n";
    }
    stream($fh);
  }
  stream($fh);
}
else
{
  $fh=get($file,$url)
    or die "Couldn't get URL!\n";
  stream($fh);
}

sub get
{
  # Open the filehandle for read and write, 
  # Lock filehandle for write,
  # fork off process to start the download.
  #   Child Process: Download URL,
  #                  Set +x bit when done
  # Return dup of filehandle
}

sub stream
{
  # Keep streaming data from filehandle until
  # the executable bit is set.  Works pretty much like
  # tail -f.
}