collections.Group

{{ $new := site.RegularPages | first 10 | group "New" }}
{{ $old := site.RegularPages | last 10 | group "Old" }}
{{ $groups := slice $new $old }}
{{ range $groups }}
  <h3>{{ .Key }}{{/* Prints "New", "Old" */}}</h3>
  <ul>
    {{ range .Pages }}
      <li>
        <a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a>
        <div class="meta">{{ .Date.Format "Mon, Jan 2, 2006" }}</div>
      </li>
    {{ end }}
  </ul>
{{ end }}