request switch statement with common block

[Andrej Mitrovic]

On Saturday, 3 August 2013 at 14:38:48 UTC, JS wrote:
>
> switch (cond)
>     common: always executed code here
>     case A : etc...
>     ....
> }
>
> instead of
>
> if (cond) { always executed code here  }
> switch (cond)
>     case A : etc...
>     ....
> }
>
> which requires modification of the condition twice when 
> necessary

Can you give a real-world example, I'm not sure what's requested 
here?