Mathematica doesn't suck, it is just an extremely large language and it takes years to learn how to use it properly. Anyway, to solve your first problem, add t

Mathematica doesn't suck, it is just an extremely large language and it takes years to learn how to use it properly. Anyway, to solve your first problem, add the definition f[_]:= Throw["Your error message here"} To solve your second problem, use Block instead of Module (though in your simple example given here the solution is to just use neither).