How to add nofollow to breadcrumb links?

Hi,

I have the following in my template.php but was wondering how I can edit it to nofollow all of the links in the breadcrumb?

function phptemplate_breadcrumb($breadcrumb) {
  if (!empty($breadcrumb)) {
    // remove the Home link
    $old_home_link = array_shift($breadcrumb);
    // insert the new link
    array_unshift($breadcrumb, l(t(''), '<front>'));
    return '<div class="breadcrumb">'. implode('', $breadcrumb) .'</div>';
  }
}

Thanks to anyone that can help.