irule to remove www. prefix from URIs

Here you go:

when HTTP_REQUEST {

    Check if the host starts with www.
   if {[string tolower [HTTP::host]] starts_with "www."}{

       Redirect with the www. prefix removed to the same URI
      HTTP::redirect "http://[string range [HTTP::host] 4 end][HTTP::uri]"
   }
}

If this is for HTTPS, your cert is only valid for example.com and the client requests www.example.com, this iRule won't prevent a cert mismatch warning. You'd also need to change the redirect from http:// to https://.

Aaron