# phpman > perldoc > Test2::Util::ExternalMeta

## NAME
    [Test2::Util::ExternalMeta](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AUtil%3A%3AExternalMeta/markdown) - Allow third party tools to safely attach meta-data to your
    instances.

## DESCRIPTION
    This package lets you define a clear, and consistent way to allow third party tools to attach
    meta-data to your instances. If your object consumes this package, and imports its methods, then
    third party meta-data has a safe place to live.

## SYNOPSIS
        package [My::Object](https://www.chedong.com/phpMan.php/perldoc/My%3A%3AObject/markdown);
        use strict;
        use warnings;

        use [Test2::Util::ExternalMeta](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AUtil%3A%3AExternalMeta/markdown) qw/meta get_meta set_meta delete_meta/;

        ...

    Now to use it:

        my $inst = [My::Object](https://www.chedong.com/phpMan.php/perldoc/My%3A%3AObject/markdown)->new;

        $inst->set_meta(foo => 'bar');
        my $val = $inst->get_meta('foo');

WHERE IS THE DATA STORED?
    This package assumes your instances are blessed hashrefs, it will not work if that is not true.
    It will store all meta-data in the "_meta" key on your objects hash. If your object makes use of
    the "_meta" key in its underlying hash, then there is a conflict and you cannot use this
    package.

## EXPORTS
    $val = $obj->meta($key)
    $val = $obj->meta($key, $default)
        This will get the value for a specified meta $key. Normally this will return "undef" when
        there is no value for the $key, however you can specify a $default value to set when no
        value is already set.

    $val = $obj->get_meta($key)
        This will get the value for a specified meta $key. This does not have the $default overhead
        that "meta()" does.

    $val = $obj->delete_meta($key)
        This will remove the value of a specified meta $key. The old $val will be returned.

    $obj->set_meta($key, $val)
        Set the value of a specified meta $key.

## META-KEY RESTRICTIONS
    Meta keys must be defined, and must be true when used as a boolean. Keys may not be references.
    You are free to stringify a reference "$ref" for use as a key, but this package will not
    stringify it for you.

## SOURCE
    The source code repository for Test2 can be found at <http://github.com/Test-More/test-more/>.

## MAINTAINERS
    Chad Granum <<exodist@cpan.org>>

## AUTHORS
    Chad Granum <<exodist@cpan.org>>

## COPYRIGHT
    Copyright 2020 Chad Granum <<exodist@cpan.org>>.

    This program is free software; you can redistribute it and/or modify it under the same terms as
    Perl itself.

    See <http://dev.perl.org/licenses/>