Side Bar category Filtering

Hi,

Trying to see how I can go further in filtering the side bar.
Here are some of the things i’m trying to do..

1.Filter by slug , now for this I think I’m close . I need it to check for partial name of the slug since slugs need to be unique.. for example

wp_list_categories(‘orderby=name&show_count=0&slug=”%cars%”&title_li=<h2>test</h2>’);

This should only display categories with the slug “cars” with in the string. such as the slug fast-car or honda-car etc etc but it doesnt work .. yet I can say slug=”honda-car” and it will indeed display the the category with the post that has the slug=”honda-car”

2.Filter by tags, ie only display categories with certain tags something like this wp_list_categories(‘orderby=name&show_count=0&tag=”displayme”&title_li=<h2>test</h2>’);

3.Filter by customfield
wp_list_categories(‘orderby=name&show_count=0&customfield=”displayme”&title_li=<h2>test</h2>’);

I think this would be useful for a lot people. If anyone can help that would be awesome and if I figure out any of these I’ll post the answers here.

Thanks