HTTP::cookie, SWITCH and multiple identical pools

Just apply a persistence cookie profile to your virtual

Then the iRule would be;-

when HTTP_REQUEST {
    foreach ck [HTTP::cookie names] {
        if {$ck starts_with "BIGipServer"} {
             Select pool based on part of cookie name
            pool [substr $ck 11]
             Drop out of event - F5 will choose appropriate pool member based on cookie
            return
        }   
    }   
    switch -glob [string tolower [HTTP::path]] {
        "/pool_a*" {
            HTTP::path "/"
            pool "pool_a" } 
        "/pool_b*" {
            HTTP::path "/"
            pool "pool_b" }
        "/pool_c*" {
            HTTP::path "/"
            pool "pool_c" } 
        "/pool_d*" {
            HTTP::path "/"
            pool "pool_d" } 
        default { reject }
       } 
    }
}