Steven Sanderson provides a quick guide to regular expressions:
Regular expressions, often abbreviated as regex, are powerful tools used in programming to match and manipulate text patterns. While they might seem intimidating at first, regular expressions are incredibly useful for tasks like data validation, text parsing, and pattern matching. In this blog post, we’ll explore regular expressions in the context of R programming, breaking down the concepts step by step and providing practical examples along the way. By the end, you’ll have a solid understanding of regular expressions and be ready to apply them to your own projects.
This is an extremely powerful language which can take years (decades?) to master, especially considering that there are several regular expression syntaxes and they don’t all behave the same way. But still, I’ve found that the more familiar you are with regular expressions, the simpler certain classes of problem become.