You probably read it correctly the first time. There are two functions: set_heroku_vars_changed, which sets the heroku_vars_changed variable, and run_heroku_config_if_settings_changed, which calls set_heroku_vars_changed and then configures Heroku if the heroku_vars_changed variable is true. The former function is basically a private function. The script calls just one thing, run_heroku_config_if_settings_changed. That handles everything.