Possible to modify function variables inside of lambda function?

Is it possible to modify a function-stack variable from inside of a lambda function?

i've tried everything I can think of.

I want to do something like this:
Create Variable: as foo
Lambda function {
$var.foo = 'testing';
}

Response: return var:foo[Screen Shot 2022-04-21 at 12.52.19 AM.png]
the value persists inside of the lambda function, but disappears outside of it.