/* get a page's language (Don't use page.language!) */
var uri = Uri.Parts(Page.uri);
var lang = uri.path[0];
if(string.Contains(lang, "project") || string.Contains(lang, "Project")) {
 let lang = string.Substr(lang, 8);
}

/* assume English */

var nextStr = 'Next »';

/* fix for other languages */

if (!string.compare(lang, "de", true)) {
  let nextStr = "weiter »";
} else if (!string.compare(lang, "es", true)) {
  let nextStr = "Siguiente »";
} else if (!string.compare(lang, "ja", true)) {
  let nextStr = "次 »";
} else if (!string.compare(lang, "ko", true)) {
  let nextStr = "다음 »";
} else if (!string.compare(lang, "pl", true)) {
  let nextStr = "Następny »";
} else if (!string.compare(lang, "ru", true)) {
  let nextStr = "Следующая статья »";
} else if (!string.compare(lang, "fr", true)) {
  let nextStr = "Suivant »";
} else if (!string.compare(lang, "zh-tw", true)) {
  let nextStr = "次頁 »";
}

<div class="prevnext">
<p align="right">(web.link(wiki.uri(lang .. '/' .. $0), nextStr))</p>
</div>
<br />