Given a list of perl modules/filenames, devel::hide 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 original intent of devel::hide 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.