NAME
    Const::Exporter - export constants

SYNOPSIS
    Define a constants module:

      package MyApp::Constants;

      use Const::Fast;

      const our $zoo => 1234;

      use Const::Exporter

         tag_a => [                  # use MyApp::Constants /:tag_a/;
            'foo'  => 1,             # exports "foo"
            '$bar' => 2,             # exports "$bar"
            '@baz' => [qw/ a b c /], # exports "@baz"
            '%bo'  => { a => 1 },    # exports "%bo"
         ],

         tag_b => [                  # use MyApp::Constants /:tag_b/;
            'foo',                   # exports "foo" (same as from ":tag_a")
            '$zoo',                  # exports "$zoo" (as defined above)
         ];

      # `use Const::Exporter` can be specified multiple times

      use Const::Exporter

         tag_b => [                 # we can add symbols to ":tab_b"
            'moo' => $bar,          # exports "moo" (same value as "$bar")
         ],

         enums => [

           [qw/ goo gab gub /] => 0, # exports enumerated symbols, from 0..2

         ],

         default => [qw/ fo $bar /]; # exported by default

    and use that module:

      package MyApp;

      use MyApp::Constants qw/ $zoo :tag_a /;

      ...

DESCRIPTION
    This module allows you to declare constants that can be exported to
    other modules.

    To declare constants, simply group then into export tags:

      package MyApp::Constants;

      use Const::Exporer

        tag_a => [
           'foo' => 1,
           'bar' => 2,
        ],

        tag_b => [
           'baz' => 3,
           'bar',
        ],

        default => [
           'foo',
        ];

    Constants in the "default" tag are exported by default (that is, they
    are added to the `@EXPORTS' array).

    When a constant is already defined in a previous tag, then no value is
    specified for it. (For example, "bar" in "tab_b" above.)

    Your module can include multiple calls to `use Const::Exporter', so that
    you can reference constants in other expressions, e.g.

      use Const::Exporter

        tag => [
            '$zero' => 0,
        ];

      use Const::Exporter

        tag => [
            '$one' => 1 + $zero,
        ];

    Constants can include traditional constant symbols, as well as scalars,
    arrays or hashes.

    Constants can include values defined elsewhere in the code, e.g.

      our $foo;

      BEGIN {
         $foo = calculate_value_for_constant();
      }

      use Const::Exporer

        tag => [ '$foo' ];

    Note that this will make the symbol read-only. You don't need to
    explicitly declare it as such.

SEE ALSO
    See Exporter for a discussion of export tags.

  Similar Modules
    Exporter::Constants
    Constant::Exporter
    Constant::Exporter::Lazy

  Modules for Declaring Readonly values
    constant
    enum
    Const::Fast
    Readonly
    Readonly::Enum

AUTHOR
    Robert Rothenberg, `<rrwo at cpan.org>'

LICENSE AND COPYRIGHT
    Copyright 2014 Robert Rothenberg.

    This program is free software; you can redistribute it and/or modify it
    under the terms of the the Artistic License (2.0). You may obtain a copy
    of the full license at:

    http://www.perlfoundation.org/artistic_license_2_0

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    Versions is governed by this Artistic License. By using, modifying or
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    by someone other than you, you are nevertheless required to ensure that
    your Modified Version complies with the requirements of this license.

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    patent license to make, have made, use, offer to sell, sell, import and
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    licensable by the Copyright Holder that are necessarily infringed by the
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