Xporter provides EXPORT functionality similar to Exporter with some different
rules to simplify common cases.

The primary difference, in Xporter is that the default EXPORT list remains the
default EXPORT list unless the user specifically asks for it to not be included,
whereas in Exporter, asking for any additional exports from the EXPORT_OK list,
clears the default EXPORT list.

Xporter makes it easy to reset or clear the default so that choice is left to
the user.

To reset the default EXPORT list to empty, a bare minus ('-') or logical-not
sign ('!') is placed as the first parameter in the client's import list.
