Re-write works with one URI but the other

when HTTP_REQUEST {
   log local0. "original URI: [HTTP::uri]"
   switch -glob [HTTP::uri] {
      "/a22/O/cd/wd" {
         set xyz [HTTP::header "abc"]
         HTTP::uri [string map "/a22/O /a22/$xyz" [HTTP::uri]]
         pool p_rewrite
         log local0. "Matched case 1"
      }
      "/a22/O/cd" {
         set abc [HTTP::header "abc"]
         HTTP::uri [string map "/a22/O /a22/$abc" [HTTP::uri]]
         pool p_rewrite
         log local0. "Matched case 2"
      }
      default {
         pool p_nonrewrite
         log local0. "Default case"
      }
   }
}
when HTTP_REQUEST priority 501 {
   log local0. "Current URI: [HTTP::uri]"
}