package Math::MyWrapper;
use Math::MyWrapper::XS();
use Exporter 'import';
our @EXPORT_OK = qw< cos ... >;
sub new {
    require Math::MyWrapper::Class;
    return "Math::MyWrapper::Class";
}
sub cos {
    my( $x ) = @_;
    return Math::MyWrapper::XS::cos( $x );
}
...