URI and Host replace

Try this:

when HTTP_REQUEST {
    switch -glob [string tolower [HTTP::uri]] {
        "/retail*" {
            pool Pool-A
            HTTP::header replace Host "b.x.com:9081"
            HTTP::uri "/portal"
        }
        "/corporate*" {
            pool Pool-B
            HTTP::header replace Host "b.x.com:9082"
            HTTP::uri "/portal"
        }
        default {
            reject
        }
    }
}