In fact, use double quotes on the right . He even pointed it out in the manual (besides having done it a hundred times), so I don’t see the problem @cwallenpool points out.
Your routing looks fine, make sure it gets called after reserved routes
$route['default_controller'] = "welcome";
$route['404_override'] = '';
$route['greeting/(:num)/(:any)'] = "greeting/index/$1/$2";
.
I suggest you try using $this->uri->rsegment(n)(info on user guide here ) to catch the adjusted uri segment that is causing you problems. (similar $this->uri->segment(n), but designed specifically for redirected URIs)
$config['uri_protocol'] AUTO PATH_INFO ( ) , . , 'index.php' $config['index_page'], htaccess index.php URL.