> But I'd like to request some general advice on local databases, meaning my own computer: no cloud, no net, no servers no mambo, I save things to disk and no one else needs to know.

I often miss questions meaning, but you can be interested in the core module Storable (but also Data::Dumper can be used for this) or CPAN Sereal and others. If you need to inspect the saved structure you can prefere YAML

See also: data-serialization-in-perl

L*