The Exporter module implements an import method which allows a module to export
functions and variables to its users' namespaces. Many modules use Exporter
rather than implementing their own import method because Exporter provides a
highly flexible interface, with an implementation optimised for the common
case.

Perl automatically calls the import method when processing a use statement for
a module. Modules and use are documented in perlfunc and perlmod. Understanding
the concept of modules and how the use statement operates is important to
understanding the Exporter.