It's a natural approach to anyone familiar with the pattern matchers explained in old Lisp books. This is not just hindsight because when I first read this chap

It's a natural approach to anyone familiar with the pattern matchers explained in old Lisp books. This is not just hindsight because when I first read this chapter in Beautiful Code I stopped after the problem statement and wrote something similar before reading the rest. (I didn't choose exactly the same grep sublanguage to implement -- it was something like supporting the most basic escaping instead of ^ and $.)