how do I append a simple URI

Nice one stjbrown. You could add a sanity check that the path doesn't already have the string as well.

Joshua, do you want to append /sc/pol to the HTTP path (/path/to/file.ext) or the URI (/path/to/file.ext?param1=value1&param2=value2)?

Here is an example of the first option:

when HTTP_REQUEST{
   if {[HTTP::host] contains "test" and not ([HTTP::path] ends_with "/sc/pol") }{

       Due to a bug in v10.0 - 10.2.1, HTTP::path truncates the HTTP query string if present.
       This is described in CR142756. This should be fixed in 10.2.1HF1.

       Check if there is a query string
      if {[HTTP::query] eq ""}{

          No query string, so append the string to the path
         HTTP::uri "[HTTP::uri]/sc/pol"

      } else {

          Append the string to the path and re-append the query string
         HTTP::uri "[HTTP::path]/sc/pol?[HTTP::query]"
      }
   }
}

And an example of the second option:

when HTTP_REQUEST{
   if {[HTTP::host] contains "test" and not ([HTTP::uri] ends_with "/sc/pol") }{
      HTTP::uri "[HTTP::uri]/sc/pol"
   }
}

Aaron