GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
gap> START_TEST("HAP library");
gap> 2simplices:= [[1,2,5], [2,5,8], [2,3,8], [3,8,9], [1,3,9], [1,4,9], [4,5,8], [4,6,8], [6,8,9], [6,7,9], [4,7,9], [4,5,7], [1,4,6], [1,2,6], [2,6,7], [2,3,7], [3,5,7], [1,3,5]];;
gap> K:=SimplicialComplex(2simplices);
Simplicial complex of dimension 2.
gap> Y:=RegularCWComplex(K);
Regular CW-complex of dimension 2
gap> STOP_TEST( "tst.tst", 1000 );