findclass function doesnt work

Correct, and it actually works that way in my tests. I'm using following config:

class hostmap {
    "test1.mm.lab,fernet.mm.lab"
    "test2.mm.lab,gin.mm.lab"
    "test3.mm.lab,rum.mm.lab"
}
rule mapper {
   redirect to "http://" + getfield(findclass(http_host, hostmap), ',', 2) +  http_uri
}
virtual 10.66.66.162:80 unit 1 {
    use rule mapper
}

Sending following request to the VIP:

GET /host.html HTTP/1.1
Host: test1.mm.lab

yields following response:

HTTP/1.0 302 Found
Location: http:///host.html
Connection: close

If I access the VIP with Firefox I get an Alert saying "www.host.html cannot be found, please check the URL and try again" and a blank window. This is what I expect because the URL in the Location header is really invalid.