Tie::Hash::MultiValue.pm 

A simple module implementing a tied class for hashes which can store 
multiple values per key. It's specifically designed to be used in code 
that was already using a standard hash and now needs to be able to store 
multiple items per key. (This is in contrast to Data::MultiValueHash, which 
creates an object which implements multiple values per key, but handles 
access via method calls rather than the standard hash interface.)

In addition, you can specify that you want only unique items to be stored;
you can even supply your own function to make the decision as to what's 
unique and what's not yourself.

See the man page for further details.

To install:

perl Makefile.PL
make
make test
make install


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