I haven’t earlier written any plugins for Textpattern despite having been using that CMS since 2005. This is extremely small plugin that was built to meet my needs: to make a title tag in lowercase letters. That’s the only functionality it offers.
How to use?
<txp:kuo_strtolower><txp:title /></txp:kuo_strtolower>
It took about two minutes to build this with the extremely helpful ied_plugin_composer.
