[CMake] "@expansion@"

[Nicolas Tisserand]

Hi all,

The following CMake script outputs "foo":

cmake_minimum_required(VERSION 2.8)
set(VAR foo)
message("@VAR@")

I'm surprised by this behavior, and could not find anything about it
in the documentation.

I'm also further confused by the parallell existence of the
string(CONFIGURE ... @ONLY@) command.

Some critical parts of the build system I'm currently working on rely
on this behavior, so I'd like to know more about it, and whether it's
here to stay.

Cheers,
Nicolas