pandoc/test/command/7582.md

% pandoc -t revealjs
# Slide

::: columns
:::: column
Left column
::::

. . .

:::: column
Right column
::::
:::
^D
<section id="slide" class="slide level1">
<h1>Slide</h1>
<div class="columns">
<div class="column">
<p>Left column</p>
</div><div class="fragment"><div class="column">
<p>Right column</p>
</div></div>
</div>
</section>