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use Attribute::Property;

...
    my $self = shift;
    ...
}

my %params = (
    type  => qr/Order|Return/,
...
# the following two method calls will fail (croaking)
$param->type = 'Ovid';
$param->month = 13;

my $param = @_ == 1 ? shift : Param::function->new({ @_ });