uri redirect to pool

That looks good. You can add a default case using the keyword default. If the string you're looking for is part of the path, you could replace HTTP::uri with HTTP::path. HTTP::path doesn't include the query string, so it might be more specific for your case.

 
 when HTTP_REQUEST { 
    switch -glob [string tolower [HTTP::path]] { 
       "*/us/*" { 
          pool pool_us 
       } 
       "*/uk/*" { 
          pool pool_uk 
       } 
       default { 
          pool default_pool 
       } 
    } 
 } 
 

Aaron