If the first argument is a function definition.

[unc0]

set-timeout #
  console.log 'test'
  , 500_ms

It won't compile.

set-timeout (#
  console.log 'test'
), 500_ms

It won't compile.

Here is my proposal:

set-timeout #{
  console.log 'test'
}, 500_ms

[kkirby]

There is actually a syntax that does work:

setTimeout(
    #
        doSomething()
    1000
)

If you provide the parenthesis, GorillaScript will treat each new line as an argument without the use of commas.