Check out http://coffeescript.org/ , particularly "The Existential Operator" (no anchor to link to sadly :():

> It's a little difficult to check for the existence of a variable in JavaScript. if (variable) ... comes close, but fails for zero, the empty string, and false. CoffeeScript's existential operator `?` returns true unless a variable is null or undefined, which makes it analogous to Ruby's nil?
> 
> It can also be used for safer conditional assignment than `||=` provides, for cases where you may be handling numbers or strings.
>
>The accessor variant of the existential operator `?.` can be used to soak up null references in a chain of properties. Use it instead of the dot accessor . in cases where the base value may be null or undefined. If all of the properties exist then you'll get the expected result, if the chain is broken, undefined is returned instead of the TypeError that would be raised otherwise.

So, `process.env.STAGEHAND_ENVIRONMENTS?` would return true/false, but `?.` is a different operator that would not access the property unless it's non null/undefined.