{
    package My::Package;
    use Moose;
    use Types::Standard qw( Bool Overload );

    has attr => (
        is     => 'ro',
        isa    => Bool | Overload["bool"],
    );

    __PACKAGE__->meta->make_immutable;
}

##</code><code>##

{
    package My::Package;
    use Moose;
    use Types::Standard qw( Bool Overload );

    has attr => (
        is     => 'ro',
        isa    => Bool->plus_coercions( Overload["bool"], sub { !!$_  } ),
        coerce => 1,
    );

    __PACKAGE__->meta->make_immutable;
}