The Twital instruction for Twig set tag is the t:set attribute.

You can use set to assign variables. The syntax to use the set attribute is:

<p t:set=" name = 'tommy' ">Hello {{ name }}</p>
<p t:set=" foo = {'foo': 'bar'} ">Hello {{ foo.bas }}</p>
<p t:set=" name = 'tommy', surname='math' ">
    Hello {{ name }} {{ surname }}


For more information about the set tag, please refer to Twig official documentation.