In March I wrote The Perl debugger can be your superpower, introducing the step debugger as a better way to debug your Perl code rather than littering your source with temporary print statements or logging. I use the debugger all the time, and I've realized that some more techniques are worth covering.
Although I mentioned a caveat when debugging web applications, our apps at work all adhere to the Perl Web Server Gateway Interface (PSGI) specification and thus we can use tools like Test::WWW::Mechanize::PSGI or Plack::Test to run tests and debugging sessions in the same Perl process. (Mojolicious users can use something like Test::Mojo for the same effect.)