Inserting attributes into the check table from Perl?

Hello all, I've just finished writing a perl program to give a user a different speed of service based on their accounting total for the last month in MySQL, and I'd like to also assign these users an IP based on this usage too. I wanted to do this by setting the Pool-Name check value from my script, after it's figured out what group the user being authenticated falls under. However, apparently the $RAD_CHECK hash is read-only. How do I write to the Check table from perl? Is it possible? Is there a way of invoking ip_pools from perl? thanks, Jan