Parse custom html tags?

[eluser]mscahill[/eluser]
I took a look at CI's template parser, but this isn't going to fit my need on this project. I need to parse my custom tags before they ever get to the view. Here's an example of what I'm looking to do:

A custom tag like this would load a resultset into an array:

Code:

<query variable='users'>SELECT * FROM users</query>

Then a result (the username for user with ID of 12) could be accessed like so:

Code:

<var:users row='12' col='user_name' />

output:

Code:

Bobby

I would also need a tag like this to forward to my drilldown controller:

Code:

<drilldown name='user' value='Bobby'>Bobby</drilldown>

output:

Code:

<a href='http://example.com/drilldown/user/Bobby'>Bobby</a>

Any ideas? I've looked at regex, PHP DOM, etc. but don't know how I would accomplish something like this.