Such expressions are likely to be generated. In fact, the Python issue refers to a lexer for javascript. Imagine your design is to have one capturing group fo

Such expressions are likely to be generated. In fact, the Python issue refers to a lexer for javascript. Imagine your design is to have one capturing group for each different language keyword, and suddenly it doesn't seem so silly any longer. https://bugs.python.org/issue22437 https://bugs.python.org/issue22437