Use the with tag to create a new inner scope. Variables set within this scope are not visible outside of the scope:
{% with %}
{% set foo = 42 %}
{{ foo }} {# foo is 42 here #}
{% endwith %}
{# foo is not visible here any longer #}
Instead of defining variables at the beginning of the scope, you can pass a hash of variables you want to define in the with tag; the previous example is equivalent to the following one:
{% with { foo: 42 } %}
{{ foo }} {# foo is 42 here #}
{% endwith %}
{# foo is not visible here any longer #}
{# it works with any expression that resolves to a hash #}
{% set vars = { foo: 42 } %}
{% with vars %}
...
{% endwith %}
By default, the inner scope has access to the outer scope context; you can disable this behavior by appending the only keyword:
{% set bar = 'bar' %}
{% with { foo: 42 } only %}
{# only foo is defined #}
{# bar is not defined #}
{% endwith %}