{{ $args := . }}
{{ $parts := split .Inner "\n---\n"  }}
<div class="side-by-side">
  {{ range $i, $part := $parts }}
    {{ $lang := $args.Get $i }}
    <div lang="{{ $lang }}">
      <header>{{ index site.Data.localeNames $lang }}</header>
      {{ $part | markdownify }}
    </div>
  {{ end }}
</div>