Another tool to debug your Plack application is InteractiveDebugger You can dive into your code, explore your stack and see all variables in each frame. And execute arbitrary code at some level! Just try it: plackup idebug-demo.psgi firefox http://127.0.0.1:5000/ D command shows all variables in frame and you can just dump any variable using Data::Dumper: perl> Data::Dumper::Dumper $self; It would