The Devel::DProf module can produce a text outline showing which functions are called from where. dprofpp -t -p myscript.pl

You could probably feed a parsed version of that text output into one of the Chart:: or Graph:: modules if you wanted a pretty chart...

However, note that this only shows the actual execution path, not all of the possible options, so you'll need to re-run your script multiple times with different inputs to see the various execution trees that result. I don't believe there's any way to generate a graph showing all of the possible ways it could flow.