* Run perl -c on every t/*.t file as a fast pre-check before prove.
* Add Perl::Critic (a curated policy set) and perltidy --check for the Perl test code — the repo lints its bash with shellcheck but has zero linting for its Perl.
* Add Test::NoWarnings (and/or Test::Fatal) to the test harness so warnings/exceptions in the code under test fail the build.
Not yet sure about using the hash / SHA-pinning. To be reconsidered later
Dirk Wetter