canjs/canjs

In my projekt I have a Map with different countries that have different products and different languages. We also have a map with the translations.
I would like to do something like this in the template:
{{vLang[vCountry]}}
I also tried with helpers but could not succeed.

Here is a simplified idea. I hope it explains the problem:

import oneTemplate from 'onetemplate.stache!';

var lang = new can.Map({
    "en": {
        "book": "book",
        "tree": "tree",
        "green": "green"
    },
    "de": {
        "book": "Buch",
        "tree": "Baum",
        "green": "grün"
    }
});

var country = can.compute("en");

$('body').html( oneTemplate({
    vLang: lang,
    vCountry: country
}) );

//stache template onetemplate.stache

{{vLang[vCountry]}}