wplist

<?php
add_shortcode('my_shortcode', 'my_shortcode_function' );
function my_shortcode_function($atts, $content) {
    $content_array = preg_split('~\s*,\s*~', $content);
    $return_array = array();
    foreach($content_array as $arr){
        $return_array[] = '<span class="myclass">'.$arr.'</span>';
    }
    return implode($return_array);
}