How do I change debug mode with dub?

[Gary Willoughby via Digitalmars-d-learn]

On Wednesday, 16 September 2015 at 10:42:13 UTC, Alex_Freeman 
wrote:
> Hey all! I'm just wondering how to run dub with different debug 
> versions, or running it with different versions generally? Is 
> there also a way to have code behind multiple debug versions, 
> or run more than one debug version at once?
>
> Thanks!

There's lots of useful information here:
http://code.dlang.org/package-format?lang=json