Portion of iRule not being processed

My other iRule that uses if statements - it is only working with uppercase.

I was able to get everything to work by removing the string tolower, and adding in an additional switch statement for both uppercase and lowercase. I can't explain why this works, but string tolower is not working. Here is the complete code that works now:

 Check the Host header value, set to lowercase
   switch -glob [string tolower [HTTP::host]] {
      "oldforum.olddomain.com" {
         switch -glob [HTTP::query] {
            "TID=*" {
               log local0. "Query string of URI [HTTP::uri] is [URI::query [HTTP::uri]]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] TID]"
               return
            }
            "tid=*" {
               log local0. "Query string of URI [HTTP::uri] is [URI::query [HTTP::uri]]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] tid]"
               return
            }
            "FID=*" {
               log local0. "Query string of URI [HTTP::uri] is [URI::query [HTTP::uri]]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] FID]"
               return
            }
            "fid=*" {
               log local0. "Query string of URI [HTTP::uri] is [URI::query [HTTP::uri]]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] fid]"
               return
            }
            "C=*" {
               log local0. "Query string of URI [HTTP::uri] is [URI::query [HTTP::uri]]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] C]"
               return
            }
            "c=*" {
               log local0. "Query string of URI [HTTP::uri] is [URI::query [HTTP::uri]]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] c]"
               return
            }
         }
      }