iRule based on domain

This example of how i think it should be, not sure this is the right way to do it:

when HTTP_REQUEST {
    if { [HTTP::header exists Origin] } {
        set origin_host [HTTP::header Origin]
    }
}
when HTTP_RESPONSE {
    if { [info exists origin_host] } {
        if { $origin_host contains "mydomain1.com, mydomain2.com, mydomain3.com" } {
           pool $HTTP_pool
        } else {
    HTTP::respond 403  
    }
    }
}