As a tester, I like to know how things work. So when I started investigating the basis for the tool Cucumber, I came across the concept of Gherkin. That was written with the help of a system call Ragel. What I was curious about was whether I could build one of these languages on my own, perhaps for a customized testing tool. This caused me to stumble upon Rex and Racc, which are two Ruby-based tools that help you build your own languages. The documentation on these tools, however, is on the bad side of awful. This post is purely to document and share what I learned.