Mobile iRule help to stay on MainSite

Try this:

when HTTP_REQUEST {
    if { [string tolower [HTTP::host]] contains "www.mysite.com" } {
        switch -glob [string tolower [HTTP::header User-Agent]] {
            "*androind*mobile*" -
            "*iphone*" -
            "*ipod*" {
                if { [HTTP::cookie exists stop_mobi] } {
                     cookie exists - do nothing (stay here)
                    return
                } else {
                    switch [URI::query [HTTP::uri] stop_mobi] {
                        "yes" {
                             URI exists and equals "yes"
                            set stop_mobi_cookie 1
                        }
                        default {
                             URI doesn't exist - redirect
                            HTTP::redirect "https://m.mysite.com"
                            TCP::close
                            event disable
                        }
                    }
                }               
            }
        }
    }
}
when HTTP_RESPONSE {
    if { [info exists stop_mobi_cookie] } {
        unset stop_mobi_cookie
        HTTP::cookie insert name stop_mobi value 1
    }
}