```
$ cat Envfile
your-heroku-app-name:
  LANG: ja_JP.UTF-8
$ heroku config -a your-heroku-app-name
=== your-heroku-app-name Config Vars
LANG: en_US.UTF-8
$ ruby path/to/heroku_config.rb # dry run
I, [2015-09-04T19:13:17.972419 #14090]  INFO -- : your-heroku-app-name
I, [2015-09-04T19:13:17.972511 #14090]  INFO -- :   C LANG=ja_JP.UTF-8
$ ruby path/to/heroku_config.rb -a # apply to heroku app
I, [2015-09-04T19:13:17.972419 #14090]  INFO -- : your-heroku-app-name
I, [2015-09-04T19:13:17.972511 #14090]  INFO -- :   C LANG=ja_JP.UTF-8
$ heroku config -a your-heroku-app-name
=== your-heroku-app-name Config Vars
LANG: ja_JP.UTF-8
$ ruby path/to/heroku_config.rb -a # apply to heroku app
I, [2015-09-04T19:13:17.972419 #14090]  INFO -- : your-heroku-app-name
I, [2015-09-04T19:13:17.972511 #14090]  INFO -- :   Nothing to change
```