Rewriting Attributes with Freeradius

Hi there, i looked around and found nothing which really helped, so i'll ask you :) I want my freeradius to rewrite the vlan attributes for cetrain clients. Setup is like having all users in my ldap, with vlan etc. and all is working fine so far. Now i have an office which has other vlans due to an migration than the main office. Now i want my vlan IDs rewritten by freeradius for that office.

From what i have read, i can do it with rlm_perl or maybe with rlm_attr_rewrite, but i didn't found anything about how exactly... If someone could point me to a doc or so, would be really nice.

Thanksalot! (especially for the freeradius itself :)