Emulating multiple attributes

attribute.pl

has config => (
    traits => ['Hash'],
    is     => 'bare',
    isa    => 'HashRef[Str]',
    lazy   => 1,

    # returns a hashref of key/value config pairs
    builder => 'load_config',

    handles => {

        has_author => [ exists => 'author' ],
        author     => [ get    => 'author' ],
        has_email  => [ exists => 'email'  ],
        email      => [ get    => 'email'  ],
    },
);

foo.pl

my $foo = Foo->new();

$foo->has_author;
$foo->author;
$foo->has_email;
$foo->email;

one.pl

has author => (
    is        => 'ro',
    isa       => 'Str',
    lazy      => 1,
    predicate => 'has_author',
    default   => sub { shift->load_config->{author} },
);

sub load_config {
    my ($self) = @_;

    ... some operation to load a config ...

    return $config_hashref;
}

silly.pl

has author => (
    is        => 'ro',
    isa       => 'Str',
    lazy      => 1,
    predicate => 'has_author',
    default   => sub { shift->load_config->{author} },
);

has email => (
    is        => 'ro',
    isa       => 'Str',
    lazy      => 1,
    predicate => 'has_email',
    default   => sub { shift->load_config->{email} },
);

sub load_config {
    my ($self) = @_;

    ... some operation to load a config ...

    return $config_hashref;
}