As others say, look at the examples in the forum.
When I was in the same boat – I'm still very slow at these things – I also found that it helped to look at the Opus Help file/Manual. But beyond that I went and found some web resources on regex. As this technology is widely used elsewhere, there are some good tutorials out there.
If you download and install some of the samples in the forum, you can then inspect them to see how they work.
These might be a good start:
RegExp basics: Removing characters from start/end of names
Don't just grab the "buttons", read the conversations as people chew over how best to do something. They often include useful explanations of what they are doing.