# Pastebin oxoBVqCO
$ nix eval --raw '(scopedImport { updated = "today"; posts = [{date="today"; author="manveru"; title="hello"; body="world"; }]; } ./templates/atom.tmpl)'
<?xml version='1.0' encoding='UTF-8'?>
<feed xmlns='http://www.w3.org/2005/Atom'>
  <id>tag:manveru.dev,2011:blog</id>
  <updated>today</updated>
  <title type='text'>manveru</title>
  <link rel='alternate' type='text/html' href='https://manveru.dev/blog'/>
  <link rel='self' type='application/atom+xml' href='https://manveru.dev/blog/atom.atom'/>
  <author>
    <name>Michael 'manveru' Fellinger</name>
  </author>
  <generator version="2019.08" uri="http://github.com/manveru/euphenix">Euphenix</generator>
<entry>
  <id>tag:manveru.dev,2011:blog,today</id>
  <published>today</published>
  <updated>today</updated>
  <author><name>manveru</name></author>
  <title type="text">hello</title>
  <content type="html">world</content>
</entry>
</feed>

$ cat templates/atom.tmpl                                       
''
<?xml version='1.0' encoding='UTF-8'?>
<feed xmlns='http://www.w3.org/2005/Atom'>
  <id>tag:manveru.dev,2011:blog</id>
  <updated>${ updated }</updated>
  <title type='text'>manveru</title>
  <link rel='alternate' type='text/html' href='https://manveru.dev/blog'/>
  <link rel='self' type='application/atom+xml' href='https://manveru.dev/blog/atom.atom'/>
  <author>
    <name>Michael 'manveru' Fellinger</name>
  </author>
  <generator version="2019.08" uri="http://github.com/manveru/euphenix">Euphenix</generator>
  '' + (__concatStringsSep "\n" (map (post: ''
    <entry>
      <id>tag:manveru.dev,2011:blog,${ post.date }</id>
      <published>${ post.date }</published>
      <updated>${ post.date }</updated>
      <author><name>${ post.author }</name></author>
      <title type="text">${ post.title }</title>
      <content type="html">${ post.body }</content>
    </entry>
  '') posts)) + ''
</feed>
''