SYNOPSIS use lib::noop qw(Foo::Bar Baz); use Foo::Bar; # now a no-op use Qux; # load as usual DESCRIPTION Given a list of module names, it will make subsequent loading of those modules a no-op. It works by installing a require hook in @INC that looks for the specified modules to be no-op'ed and return "1;" as the source code for those modules. This makes loading a no-op'ed module a success, even though the module does not exist on the filesystem. And the %INC entry for the module will be added, making subsequent loading of the same module a no-op too because Perl's require will see that the entry for the module in %INC already exists. But, since the loading is a no-op operation, no code other than "1;" is executed and if the original module contains function or package variable definition, they will not be defined. This pragma can be used e.g. for testing. To cancel the effect of lib::noop, you can unimport it. If you then want to actually load a module that has been no-op'ed, you have to delete its %INC entry first: use lib::noop qw(Data::Dumper); use Data::Dumper; # this code will die because Data::Dumper::Dumper is not defined BEGIN { print Data::Dumper::Dumper([1,2,3]) } no lib::noop; BEGIN { delete $INC{"Foo/Bar.pm"} } use Data::Dumper; # this code now runs ok BEGIN { print Data::Dumper::Dumper([1,2,3]) }