What is the utility of .stringof with expressions?

[Shriramana Sharma via Digitalmars-d]

cym13 wrote:

> It could be useful combined with mixins to preprocess the code
> you write before compiling it.

Huh? Can you give me a concrete example? I'm not being intentionally dense 
but I can't imagine such a use case where you can't just write the string 
literal yourself...

-- 
Shriramana Sharma, Penguin #395953