Open Expresso - you know, the app I suggested you install for both of your previous questions.
Now, paste the Regex into the "Regular Expression" pane:
Look to it's right at the "Regex Analyzer" pane. Expand all branches.
See how it explains what
But that Regex is useless. It explicitly capture nothing, and wouldn't work if it did since it's trying to capture two suffixes and exclude them both...