Activate the Perl::Critic policy Variables::ProhibitUnusedVariables
The policy might indicate some lines of code that can be cleaned up. The default severity is SEVERITY_MEDIUM, thus the policy does not run in the default configuration.
Let's activate this after OTOBO 10.1.1 is released and development switches to the rel-11.0.x branch.
See https://metacpan.org/pod/Perl::Critic::Policy::Variables::ProhibitUnusedVariables