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