yko

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 be great to have perl debugger-like alias 'x' for this command, maybe it will appear in future.