Port Redirection Failure

You can't use the

pool

command in LB_SELECTED as the load balancing decision has already been made. Try placing your pool command in HTTP_REQUEST

(you also had a missing end quote in the switch)

https://devcentral.f5.com/wiki/iRules.pool.ashx

when HTTP_REQUEST {
    switch -glob [HTTP::uri] {
        "/App1*" {
            set port 80
        }
        "/App2*" {
            set port 81
        }
        "/App3*" {
            set port 82
        }
    }

    if {([info exists port]) && ($port ne "")}  {
        pool [LB::server pool] member [LB::server addr] $port
    }
}

PS - Pool command added inside an

if

, this is because the $port variable may not exist if a connection arrives with a different URI to the one in the switch statement. If this happens you'll get a TCL error.