iRule based on domain

Thank you for your time, however i don't understand how to fit in in my rule.. maybe someone can help me to write it correctly? Maybe i can do it simpler like this?

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" } {
           pool $HTTP_pool
           }elsif{ 
            { $origin_host contains "mydomain2.com" } {
           pool $HTTP_pool
            }elsif{ 
            { $origin_host contains "mydomain3.com" } {
           pool $HTTP_pool
        } else {
    HTTP::respond 403  
    }
    }
}