While I cannot recommend from personal experience, these seem to be
the links you need. Though I actually have a porting project that could use them I end up writing little greppy scripts that make text reports of what calls what. So for my current project besides just grepping the names of all subs in a file at the command line, I have written some utilities based on File::Find. For example make a list of all the files in all folders, sort by suffix, find callers, find all html files that call a given cgi, etc. This info is important for me to refactor it all.
in reply to Inspection/Introspection
But I was moved to check again since I remember finding (and I think mentioning on PM, somewhere..) someone who had done a cool demonstration of graphing of his perl program at runtime. I couldn't find it but think this is probably GraphViz..
Answer: Generate UML from Perl code? includes four responses including autodia.
Generate a Graph-ical call tree for your *.pm perl modules uses graphviz at AT&T.
An article at DDJ about using graphviz.
cpan search for graphviz which showed me some other things like GraphViz::ISA and Joe McMahon's site on GraphViz::Data::Structure
Hope this helps.