All too often, configuration is not a universal or one-time thing,
yet most configuration-handling treats it as such. Perhaps you can
only load one config file. If you can load more than one, you often
have to load all of them at the same time or each is stored completely
independently, preventing one from being able to override another.
Config::Onion changes that.

Config::Onion stores all configuration settings in four layers:
Defaults, Main, Local, and Override. Each layer can be added to as
many times as you like. Within each layer, settings which are given
multiple times will take the last specified value, while those
which are not repeated will remain untouched.

Homepage:
https://metacpan.org/pod/Config::Onion
