Data::Transformator, Data::Merger, Data::Comparator perform
intelligent operations on nested perl data structures.  The
transformation engine is a general simple transformation engine and
can run in a selective mode or a constructive mode.  In the selective
mode, it behaves like a database query engine.  In the constructive
mode it constructs a result based on the structure of the original
data.  Transformations can be cascaded.  The merger also deals with
general nested perl data structures.  The Comparator generates
structured differences that mirror the structure of the compared data
structures.

To install the module...

perl Makefile.PL
make
make test
make install

If you are on a windows box you should use 'nmake' rather than 'make'.