Not sending traffic to first pool

==== String Data Groups defined in the GUI ====
class hosts_to_cache {
  "www.website.com"
  "XX.XX.XX.XX"
}
class file_types_to_cache {
  ".gif"
  ".jpg"
  ".GIF"
  ".JPG"
}
==== iRule ====
when HTTP_REQUEST {
   Note: I replaced "contains" with "equals" here since
   more than likely you want to do a full string compare
   on the host name.  Change back to "contains" if you want
   to cover extensions of those host names
  if { [matchclass [HTTP::host] equals $::hosts_to_cache] } {
    if { [matchclass [HTTP::uri] ends_with $::file_types_to_cache] } {
      pool edge-fx
    } else {
      pool web-pool
    }
  } else {
     Just pointing out here that you left out the else clause 
     of the first if.
  }
}