Yes, in general one is better off to

• always default to private vars with my
• only use public our when really needed

But this is not always so, there are always exceptions to the rule.

Some modules use package vars for external config, e.g. Text::Glob or Data::Dumper °

Some even export readonly vars to be used as constants (instead of barewords without sigils)

°) of course TIMTOWTDI, these design patterns date back to the Perl4 times, which had neither OOP nor private lexical vars. Data::Dumper for instance has a dual API.