your question is a little smoky, for me.

Config::Any and Config::General and JSON::MaybeXS are valid options to have a separate configuration.

Also YAML can be used to have separate configuration.

But perhaps it is better to specify to us what makes machine X different from machine A. Many modules has builtin for configuration using some exported (or anyway accessible using the full package qualified name) variable. This can sounds weird to someone but is, imhe, a frequent thing.

Many others use effective %ENV vars to change their behaviour; this is vary basic but valid too.

L*