Is it possible to pass variable as reference?

[qw23]

Like this?

The input variable is typed as “Any (unevaluated)”, hence the ƛ (lambda):

or:

What does "(Unevaluated)" in an input type name mean?

Ordinarily, like most but not all programming languages, Snap! evaluates the inputs to a procedure before calling the procedure itself. That is, when you say [untitled script pic] procedure FOO knows that the value of its input is 5, but it doesn't know how that input was computed. It doesn't know that there's an addition involved; as far as FOO is concerned, it would make no difference if the expression were [untitled script pic (1)] This evaluation rule (evaluate inputs first) is called …