unset(n) on macOS
The text a7d51b6cddf5, as Mac OS X 10.2.2, Mac OS X 10.2.1, Mac OS X 10.2, Mac OS X 10.1.5, Mac OS X 10.1.4, Mac OS X 10.1.3, Mac OS X 10.1.2, Mac OS X 10.1.1, Mac OS X 10.1, Mac OS X 10.0.4, Mac OS X 10.0 shipped it.
Delete variables