Rewrite URL and change pool trouble

In your HTTP::uri command, you are referencing a variable named "uri". This will be undefined unless you specifically set it with the "set" command. Also, the error for "then" is because there is no "then" reserved word. The "then" is the contents of the enclosed braces.

Also, are you sure the "string range" command is returning what you want. It's returning from the 27th character to the end of the string, or an empty string if the URI isn't 27 characters.

Give this a try.

when HTTP_REQUEST {
  if { [HTTP::uri] starts_with "/blog" } {
    HTTP::uri "/blogs/menopauseinsightblog[string range [HTTP::uri] 27 end]"
  } 
  if { [HTTP::host] eq "www.xxxxxxxxxinsight.com" } {
    HTTP::header replace "Host" "cs.geoxxxx.com"
  } elseif { [HTTP::host] eq "xxxxxxxxxinsight.com" } {
    HTTP::header replace "Host" "cs.geosign.com"
  }
  if { [HTTP::uri] contains "/blog" } {
    pool MIS-WEB21-CS
  } else {
    pool MIS-WEB20-4
  }
}

-Joe