Then maybe look at what the Perl code returns and see whether it is what you expect?

The AngularJS documentation should be clear about what it expects.

With HTTP, you can conveniently test the server side and the client side separately, and even inspect all communication between the two parts. Replace the AngularJS by manual interaction and you can test out the Perl code. Once you are satisfied that your Perl code works as it should, you can then use static files served from your webserver as responses to test your AngularJS code. It's not hard.