add header based on request

e.g.

 config

[root@ve11a:Active:In Sync] config  tmsh list ltm virtual bar
ltm virtual bar {
    destination 172.28.24.10:80
    ip-protocol tcp
    mask 255.255.255.255
    pool foo
    profiles {
        http { }
        tcp { }
    }
    rules {
        qux
    }
    source 0.0.0.0/0
    source-address-translation {
        type automap
    }
    vs-index 32
}
[root@ve11a:Active:In Sync] config  tmsh list ltm rule qux
ltm rule qux {
    when HTTP_REQUEST {
  if { [string tolower [HTTP::path]] ends_with ".xml" } {
    set add_header 1
  } else {
    set add_header 0
  }
}
when HTTP_RESPONSE {
  if { $add_header } {
    HTTP::header insert "X-Robots-Tag" "noindex"
  }
}
}

 test

[root@ve11a:Active:In Sync] config  curl -I http://172.28.24.10/1.html
HTTP/1.1 404 Not Found
Date: Mon, 26 May 2014 14:48:02 GMT
Server: Apache/2.2.3 (CentOS)
Content-Type: text/html; charset=iso-8859-1

[root@ve11a:Active:In Sync] config  curl -I http://172.28.24.10/1.xml
HTTP/1.1 404 Not Found
Date: Mon, 26 May 2014 14:48:06 GMT
Server: Apache/2.2.3 (CentOS)
Content-Type: text/html; charset=iso-8859-1
X-Robots-Tag: noindex