use Scalar::Util qw( blessed );

sub is_or_extends {
    my ($type) = @_;

    croak "is_or_extends() expects a package name"
        if !defined($type) || ref($type) ne '';

    return sub {
        return ( blessed($_[0])
           ? $_[0]->isa($type)
           : UNIVERSAL::isa($_[0], $type)
        );
    };
}