Ok figured it out for myself, here's the code that actually works:

/blog/index.php:

<?php
perch_blog_custom([
  'count' => 10,
  'sort' => 'postDateTime', 
  'sort-order' => 'DESC',
  'each' => function($item) {
    $item['tags_html'] = perch_blog_post_tags($item['postSlug'], 'post_tag_link.html', true);
    return $item;
  },
  'template' => 'post_in_list.html'
]);
?>

post_in_list.html

<perch:blog id="tags_html" encode="false" />