Help with iRule to route by host header to pool

Thanks for the help in advance!

The datagroup will be string and be formated like hostname:poolname

when HTTP_REQUEST {
 test_dg is a string data-group where the entries are name:value pairs
 name is the requested HTTP host header, value is the associated pool-name

     check the requested HTTP host header against entries in data-group
    if { [class match [string tolower [HTTP::host]] equals test_dg ] } {
         if the HTTP host header is in datagroup
         send the request to the pool associated with the datagroup entry
        pool [class match -value [string tolower [HTTP::host]] equals test_dg ]
    } else {
         drop the request if the host header is not in datagroup
        drop
}
}