The filter tag allows you to apply a filter to a large chunk of template.

twig
{% filter upper %}
    hello
{% endfilter %}}

{# output: 'HELLO' #}

Multiple filters can be chained together.

twig
{% filter upper | lower | title %}
    hello<br>
{% endfilter %}}

{# output: 'HELLO&lt;br&gt;' #}