Is there an automatic tagging plugin?

Hello,

I am looking for a way to go through a bunch of posts and auto-assign tags.

Basically what I’m thinking is, let’s say you have a bunch of posts on cooking. I could say, “if the words ‘chicken’, ‘duck’, or ‘bird’ are mentioned in the post, add the tag ‘poultry’.” same thing for beef (steak, chuck, etc). So I would enter the keywords and the resulting tag I wanted associated with those keywords and it would populate the posts.

I have seen other autotag plugins based on SEO but I haven’t seen anything like this.

If there is no such plugin, is there a hack instead?

Thanks!