this is really awesome :-)

benchmarks/boolean/compsolid.geo

@@ -4,8 +4,18 @@ Mesh.Algorithm = 6;
 Mesh.CharacteristicLengthMin = 0.1;
 Mesh.CharacteristicLengthMax = 0.1;
 
+DefineConstant[
+  sph = {0, Choices{0,1}, Name "Make sphere a single volume"}
+  xx = {2.2, Min -1, Max 5, Step 0.01, Name "Sphere position"}
+];
+
+
 Block(1) = {0,0,0, 2,2,2};
-Sphere(2) = {2.2, 1, 1, 0.5};
+Sphere(2) = {xx, 1, 1, 0.5};
 Block(3) = {2,0,0, 4,2,2};
 
 BooleanFragments { Volume{1}; Delete; }{ Volume{2,3}; Delete; }
+
+If(sph)
+  BooleanUnion { Volume{2}; Delete; }{ Volume{3}; Delete; }
+EndIf