Override Config variable in Laravel 5.1

In my config/app.php file, I have added some variable and I have used these variable in my controller and view files. See below variables:

'META_TITLE' => 'title'
'META_KEYWORDS' => 'keyword'
'META_DESCRIPTION' => 'description'

and I have used these variables like this Config::get("app.META_TITLE")

But I want to override those variable in any of my controller as per requirement.

via Chebli Mohamed