As far as I know there is no translation for ** int or * int [] defined in the standard typemap.

You'll have to either add some kind of entry to your local typemap file that makes sense for you, or add a function in your XS code that calls the jwcmp function with arguments and/or return values that are intelligible to perl (which boils down to more or less the same thing, only a single XS function doesn't have to be generic and it's a bit easier to write)