For example, below I have a form login HTTP request and I need to evaluate the HTTP response code/status if I should continue with the next request.
I added a regular expression extractor to the HTTP request I want to evaluate, choose response code and get the 3 digit via regex -> (...) and map it to variable name "status"
After that, I add an "if controller" as the parent of my next request, and evaluate the status with logic expression like below
