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Exporter::Easy

Takes the drudgery out of Exporting symbols

In module YourModule.pm:

  package YourModule;
  use Exporter::Easy (
    OK => [ '$munge', 'frobnicate' ] # symbols to export on request
  );

In other files which wish to use YourModule:

  use ModuleName qw(frobnicate);      # import listed symbols
  frobnicate ($left, $right)          # calls YourModule::frobnicate

Exporter::Easy makes using Exporter easy. In it's simplest case it allows you to drop the boilerplate code that comes with using Exporter, so

  require Exporter;
  use base qw( Exporter );
  use vars qw( @EXPORT );
  @EXPORT = ( 'init' );

becomes

  use Exporter::Easy ( EXPORT => [ 'init' ] );

and more complicated situations where you use tags to build lists and more tags become easy, like this

  use Exporter::Easy (
        EXPORT => [qw( init :base )],
        TAGS => [
                base => [qw( open close )],
                read => [qw( read sysread readline )],
                write => [qw( print write writeline )],
                misc => [qw( select flush )],
                all => [qw( :base :read :write :misc)],
                no_misc => [qw( :all !:misc )],
        ],
        OK => [qw( some other stuff )],
  );

This will set @EXPORT, @EXPORT_OK, @EXPORT_FAIL and %EXPORT_TAGS in the current package, add Exporter to that package's @ISA and do a "use vars" on all the variables mentioned. The rest is handled as normal by Exporter.

Put

        use Exporter::Easy ( KEY => value, ...);

in your package. Arguments are passes as key-value pairs, the following keys are available

The value should be a reference to a list that goes like (TAG_NAME, TAG_VALUE, TAG_NAME, TAG_VALUE, ...), where TAG_NAME is a string and TAG_VALUE is a reference to an array of symbols and tags. For example 

  TAGS => [
    file => [ 'open', 'close', 'read', 'write'],
    string => [ 'length', 'substr', 'chomp' ],
    hash => [ 'keys', 'values', 'each' ],
    all => [ ':file', ':string', ':hash' ],
    some => [':all', '!open', ':hash'],
  ]

This is used to fill the %EXPORT_TAGS in your package. You can build tags from other tags - in the example above the tag "all" will contain all the symbols from "file", "string" and "hash". You can also subtract symbols and tags - in the example above, "some" contains the symbols from all but with "open" removed and all the symbols from "hash" removed.

The rule is that any symbol starting with a ':' is taken to be a tag which has been defined previously (if it's not defined you'll get an error). If a symbol is preceded by a '!' it will be subtracted from the list, otherwise it is added.

If you try to redefine a tag you will also get an error.

All the symbols which occur while building the tags are automatically added your package's @EXPORT_OK array.

The value should be a reference to a list of symbols and tags (which will be exapanded). These symbols will be added to the @EXPORT_OK array in your package. Using OK and and OK_ONLY together will give an error.
The value should be a reference to a list of symbols and tags (which will be exapanded). The @EXPORT_OK array in your package will contains only these symbols.. This totally overrides the automatic population of this array. If you just want to add some symbols to the list that Exporter::Easy has automatically built then you should use OK instead. Using OK_ONLY and OK together will give an error.
The value should be a reference to a list of symbol names and tags. Any tags will be expanded and the resulting list of symbol names will be placed in the @EXPORT array in your package. The tag created by the ALL key is not available at this stage.
The value should be a reference to a list of symbol names and tags. The tags will be expanded and the resulting list of symbol names will be placed in the @EXPORT_FAIL array in your package. They will also be added to the @EXPORT_OK list.
The value should be the name of tag that doesn't yet exist. This tag will contain a list of all symbols which can be exported.
If you set this to 0 then Exporter will not be added to your @ISA list.
If this is set to 1 or not provided then all $, @ and % variables mentioned previously will be available to use in your package as if you had done a "use vars" on them. If it's set to a reference to a list of symbols and tags then only those symbols will be available. If it's set to 0 then you'll have to do your own "use vars" in your package.

We need take the information provided and build @EXPORT, @EXPORT_OK, @EXPORT_FAIL and %EXPORT_TAGS in the calling package. We may also need to build a tag with all of the symbols and to make all the variables useable under strict.

The arguments are processed in the following order: TAGS, EXPORT, OK, OK_ONLY and FAIL, ALL, VARS and finally ISA. This means you cannot use the tag created by ALL anywhere except in VARS (although vars defaults to using all symbols anyway).

For details on what all these arrays and hashes actually do, see the Exporter documentation.

Written by Fergal Daly <fergal@esatclear.ie>.

Under the same license as Perl itself