Many Ruby domain-specific languages go for beauty over usability - and it shows, when you try to use them. But one of programming's oldest, most common DSLs - regular expressions - is both as ugly and as persistent as a cockroach. What makes regexes tick? By breaking down their design, we'll learn concrete principles that go deeper than "Englishy:" principles like "composability" and "deep domain integration." We'll learn how to get precise about the API design and boundaries of our DSLs. We'll write a micro-DSL that is usable without monkeypatching.`