This is Perl module Hash::FieldHash.

INSTALLATION

Hash::FieldHash installation is straightforward. If your CPAN shell is set up,
you should just be able to do

    $ cpan Hash::FieldHash

Download it, unpack it, then build it as per the usual:

    $ perl Makefile.PL
    $ make && make test

Then install it:

    $ make install

DOCUMENTATION

Hash::FieldHash documentation is available as in POD. So you can do:

    $ perldoc Hash::FieldHash

to read the documentation online with your favorite pager.

Goro Fuji