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