[_ck_]

You don’t need to tamper with the regex.

Essentially you are adding the attibutes incorrectly.

This is wrong: 'wiki' => array('a','href')

That means set a new tag called “wiki” with the attributes “a” and “href”. But really only “href” is an attribute.

I could help you more if I understood what <wiki></wiki> was supposed to do.