The debug sampler generates a sample containing all the values of JMeter variables and/or properties. A View Results Tree listener must be present in the test plan to view its results. This nifty component helps you debug your test plans appropriately, providing you with the tools to analyze the runtime-assigned values of various variables during test execution. In our aforementioned example, suppose we add a Regular Expression Extractor post processor to the /itunes/charts sampler and store it in a variable, we will be able to view the value assigned to the variable, and more importantly how to get to the different values if there is more than one match. To add a Debug Sampler, right-click on Thread Group, and navigate to Add | Sampler | Debug Sampler, as follows:

The debug sampler via the View Result Listener

As you can see from this screenshot, the multiple matches are stored under linkclass_n (where n is a match position), followed by the variable name declared in our...