{% if include.post.tags %}

<span itemprop="keywords">
  {% if include.post.tags.size == 1 %}
    <a href="{{ include.post.tags.first | tag_url }}">{{ include.post.tags.first }}.</a>
  {% else %}
    {% assign penultimate = include.post.tags.size | minus: 2 %}
    {% for i in (0..penultimate) %}
      {% if include.post.tags.size == 2 %}
        <a href="{{ include.post.tags[i] | tag_url }}">{{ include.post.tags[i] }}</a>
      {% else %}
        <a href="{{ include.post.tags[i] | tag_url }}">{{ include.post.tags[i] }},</a>
      {% endif %}
    {% endfor %}
    and <a href="{{ include.post.tags.last | tag_url }}">{{ include.post.tags.last }}.</a>
  {% endif %}
</span>

{% endif %}