I'd be suprised if anyone actually uses this package, but here's a patch to get it to build with GCC 4.x.
Created attachment 93549 [details, diff] at-poke-0.2.2-lvalue.patch
This is already fixed in at-poke-0.2.3, but I applied the patch to 0.2.2 since it's the stable version right now. Thanks for the report.