give variable to twig code example

Example 1: twig is set variable

{# defined works with variable names #}
{% if foo is defined %}
    ...
{% endif %}

{# and attributes on variables names #}
{% if foo.bar is defined %}
    ...
{% endif %}

{% if foo['bar'] is defined %}
    ...
{% endif %}

Example 2: twig set variable

{% set foo = 'bar' %}