Block specific URI

I think you're getting the TCL error because you've already issued a redirect from one rule and then are trying to insert a header in the request. If you do combine the rules, you could add them to an if/else block and eliminate this error:

when HTTP_REQUEST {
    Respond to requests for server-status
   if {[HTTP::uri] contains "server-status"} {
       Send HTTP 200 response
      HTTP::respond 200 content "Error"
   } else {
       Remove existing Client-IP headers
      while {[HTTP::header exists "Client-IP"]} {
         HTTP::header remove "Client-IP"
      }
       Insert the original client IP address in the Client-IP header
      HTTP::header insert "Client-IP" [IP::client_addr]
   }
}

Aaron