variables in a switch statement

[root@ve1023:Active] config  b virtual bar list
virtual bar {
   snat automap
   pool foo
   destination 172.28.19.79:80
   ip protocol 6
   rules myrule
   profiles {
      http {}
      tcp {}
   }
   vlans external enable
}
[root@ve1023:Active] config  b rule myrule list
rule myrule {
   when HTTP_REQUEST {
        set foo "bar"
        switch -glob -- [URI::decode [HTTP::uri]] "
                /$foo/* { HTTP::respond 200 content {you found foo.} }
        "
}
}

[root@ve1023:Active] config  curl -i http://172.28.19.79/bar/abc
HTTP/1.0 200 OK
Server: BigIP
Connection: Keep-Alive
Content-Length: 14

you found foo.