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.

The arrays @EXPORT and @EXPORT_OK in a module hold lists of symbols that are going to be exported into the users name space by default, or which they can request to be exported, respectively. The symbols can represent functions, scalars, arrays, hashes, or typeglobs. The symbols must be given by full name with the exception that the ampersand in front of a function is optional,
Eg:
@EXPORT = qw(afunc $scalar @array); # afunc is a function
@EXPORT_OK = qw(afunc $scalar @array); # afunc is a function

Exports pollute the namespace of the module user. If you must export try to use @EXPORT_OK in preference to @EXPORT and avoid short or common symbol names to reduce the risk of name clashes.

The names of any symbols that cannot be exported should be listed in the @EXPORT_FAIL array. If a module attempts to import any of these symbols the Exporter will give the module an opportunity to handle the situation before generating an error. The Exporter will call an export_fail method with a list of the failed symbols.
Eg:
@failed_symbols = $module_name->export_fail(@failed_symbols);

If the export_fail method returns an empty list then no error is recorded and all the requested symbols are exported. If the returned list is not empty then an error is generated for each symbol and the export fails. The Exporter provides a default export_fail method which simply returns the list unchanged.

Uses for the export_fail method include giving better error messages for some symbols and performing lazy architectural checks (put more symbols into @EXPORT_FAIL by default and then take them out if someone actually tries to use them and an expensive check shows that they are usable on that platform).

In reply to Re: Exporter Module by leslie
in thread Exporter Module by anbutechie

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