Just to be concrete:

sub Apache::send_range {

  my ($r,$fh, $offset, $end) = @_;

  seek($fh,$offset,0);

  my $buf;
  my $bufsiz=4096;
  my $current_position = $offset;

  my $read_size= sub {
    my $amount_to_go = ($end - $current_position);
    if ($amount_to_go <= $bufsiz) {
      $bufsiz;
    } else {
      $amount_to_go;
    }
  }

  while (read($fh,$buf,&$read_size)) {
    $current_position += &$read_size;
    $r->print($buf);
  }

}
[download]

        - tye (but my friends call me "Tye")