Given a list of Perl modules/filenames, this module makes require and use statements fail (no matter the specified files/modules are installed or not). They die with a message like: Can't locate Module/ToHide.pm (hidden) The intent of this module is to allow Perl developers to test for alternative behavior when some modules are not available. In a Perl installation, where many modules are already installed, there is a chance to screw things up because you take for granted things that may not be there in other machines.