CASE: How to print a boolean

People sometimes wonder how to print a boolean, because a boolean input doesn’t show anything by default in a pdf/preview. So the following code would be empty in a pdf:

{% input custom.some.value as:boolean %}

The easiest way to show something in the export is for example by just putting an ‘X’:

{% input custom.some.value as:boolean %}
{% nic %}
    {% if custom.some.value == 'true' %}X{% endif %}
{% endnic %}