use Module::Stubber; stub 'Foo::Bar' => { new => sub { bless {}, $_[0]; }, stringify => sub { "$_[0]"; } }; autorequire( qr/^Acme::/ => undef ); # Block access to Acme:: modules autorequire( 1 => sub { my $mod = shift; local @INC; unshift @INC,$special_lib; eval "require $mod"; !$@};