In Variational Perturbation Theory, what do small perturbations aim to do?

In Variational Perturbation Theory, small perturbations are introduced to modify or perturb a known quantum system. These perturbations can represent external influences or interactions that alter the behavior of the system. By studying the response of the system to these perturbations, we can gain insight into its properties and behavior under different conditions. This approach allows us to explore the effects of perturbations on the energy levels, wavefunctions, and other properties of quantum systems, helping us understand their behavior in various contexts.