ptkdb

Using Perl's Tk debugger, how can I set a breakpoint in my Perl library?

I have a large Perl script that is broken into several Perl libraries. In the Perl Tk debugger, I'd like to be able to set a breakpoint in one of the library files. The only way I know how to set a breakpoint in ptkdb is to navigate to the line in the source code pane. However, that source code pane only has the top level Perl script....