iRule to limit access to webserver directory by client IP

This is because you're defining an array when what you really want is a class.

You can define this in the GUI under the Data Groups section, or manually in the configuration file if you prefer, by stating a class outside of your iRule (just as you would define a VIP or a pool) like so:

class http_allowed_ip_list {
  "10.0.0.11/12"
  "10.0.0.12/13"
}

You should then be able to remove the array definition statement in your rule, and have the matchclass execute properly.

Colin