Is it possible to conditionally configure Lighttpd based on custom request headers?

It's possible to do so by IP address (and other variables):

$HTTP["remoteip"] ==  "0.0.0.0" {
    // Do something
}

Is there something similar for request headers, for example:

$HTTP["X-Some-Header"] ==  "Value" {
    // Do something
}

I don't think there is looking through documentation and searching Google, but perhaps somebody knows a way.

Thanks