This is Perl module Scalar::Util::Instance. INSTALLATION Scalar::Util::Instance installation is straightforward. If your CPAN shell is set up, you should just be able to do $ cpan Scalar::Util::Instance Download it, unpack it, then build it as per the usual: $ perl Makefile.PL $ make && make test Then install it: $ make install DOCUMENTATION Scalar::Util::Instance documentation is available as in POD. So you can do: $ perldoc Scalar::Util::Instance to read the documentation online with your favorite pager. Goro Fuji (gfx)