Data::Dumper and other modules do a great job at dumping data structures.
Their output, however, often takes more brain power to understand than the
data itself. When dumping large amounts of data, the output can be overwhelming
and it's difficult to see the relationship between each piece of the dumped
data.  Data::TreeDumper also dumps data in a tree-like fashion but hopefully
in a format more easily understood.

Data::TreeDumper also gives one extraordinary control over output and
provides for custom filtering of and iteration over data structures.