That's a handy script to keep around for sure. It might be worth pointing out to those not in the know that MetaCPAN::Client acts only on the meta data. That is, it will only report dependencies of a module which the meta data of that module declares to be dependencies. Such a list is not always correct, up-to-date, complete or even (in some cases) present at all.
For example, B::Tree uses GraphViz but doesn't declare this in its metadata, so using MetaCPAN::Client you would think it had no dependencies at all. B::Tree is far from being alone in this. The good people at CPANTS provide some statistics for this particular type of error on the part of module authors/maintainers. You'll see some of the modules on that list are recent releases and some by authors you might expect to be on top of such detail so it's a very easy human error to make. Module maintainers can always use something like Test::Prereq to help keep the dependency lists up to date.
For an end user looking to find dependencies, the lesson is to take the metadata with a pinch of salt.