This is Perl module Array::Diff.
INSTALLATION
Array::Diff installation is straightforward. If your CPAN shell is set up,
you should just be able to do
% cpan Array::Diff
Download it, unpack it, then build it as per the usual:
% perl Makefile.PL
% make && make test
Then install it:
% make install
DOCUMENTATION
Array::Diff documentation is available as in POD. So you can do:
% perldoc Array::Diff
to read the documentation online with your favorite pager.
Daisuke Murase