Using URI to rewrite host

when HTTP_REQUEST {
  set host [HTTP::host]
  set uri [HTTP::uri]
  set token [getfield [HTTP::uri] "/" 2]
   If no uri is passed in, then leave everything as is
  if { $token ne "" } {
    if { [matchclass $uri ends_with $::file_extensions] > 0 } {
       for case www.site.com/dir1/file.htm => www.site.com/dir1/file.htm
      log local0. "Found file request, leaving host and uri alone"
    } else {
      log local0. "Not a file request, update host and check for trailing slash "
       Check if host starts with token
       If not, then prepend it with the token
      if { ! ($host starts_with $token) } {
         ie. www.site.com/dir1 => dir1.www.site.com/dir1
        log local0. "Host doesn't start with token so updating host"
        set host "$token.$host"
        HTTP::header replace "Host" $host
      }
       Check if url ends with a slash
       if not, then append it with one
      if { ! ($uri ends_with "/") } {
         ie. dir1.www.site.com/dir1 => dir1.www.site.com/dir1/
        log local0. "Uri doesn't end with a slash, updating"
        append uri "/"
        HTTP::uri $uri
      }
    }
  }
  log local0. "host: $host"
  log local0. "uri : $uri"
  log local0. "full: $host$uri"
}