How and when to use a error variable qlikview

[Anonymous]

Hi Experts !!

I was working with  the "Set Statement" variables when something called my attention.

The  "error Variables"

Wondering how they worked, I set some values and forced a Error but nothing happends,

looking at the Qliview-Help its writing

Error variables

The values of all error variables will exist after the script execution. The first variable, ErrorMode, is input from the user, and the last three are output from QlikView with information on errors in the script.

But i dont really know what they mean or when to use them.

Does anyone know when and how to use them ?

Thanks in Advance

Enrique