What does func!thing mean?

[Gary Willoughby]

On Friday, 8 November 2013 at 08:59:17 UTC, Gary Willoughby wrote:
> For a friendly introduction to D template system please take a 
> look at this: http://nomad.so/2013/07/templates-in-d-explained/

Then to understand why parens are optional take a look at this: 
http://nomad.so/2013/08/alternative-function-syntax-in-d/