Irule help with creating a single VIP but with multiple pools

This is how I do what your are looking to do. I updated /blog_ to /blog* and /application_ to /application*.

when HTTP_REQUEST {
   Check requested uri header (set to lowercase)
switch -glob [string tolower [HTTP::uri]] {
    "/blog*" {
        pool bigip2
    }
    "/application*" {
        pool bigip3
    }
    default {
        pool bigip
    }
}
}