[CMake] strange construction

[Alexander Neundorf]

On Friday 12 September 2008, Aleix wrote:
> Hi list,
> I've seen on many scripts constructions like this.
>
> IF("${VAR}" MATCHES "^${VAR}$")
>
> I don't really get what it means. (in my logic would be something that
> starts and ends the same as himself)

That's from relatively old cmake times and tests whether a variable is 
undefined or just empty IIRC.

Alex