Take a look at the caller function.

About a graphical debugger, I use ptkdb; it's a visual debugger written in Perl/Tk by Andrew Page. I can't remeber if the PDF documentation is part of the package, but it exists if you need it, and it's very good. You can install it with <code>perl -MCPAN -e 'install Devel::ptkdb'.

Ciao!
--bronto