There is an importance to theoretical considerations that goes beyond their immediate practical applications. Ultimately, it comes down to how well one understa

There is an importance to theoretical considerations that goes beyond their immediate practical applications. Ultimately, it comes down to how well one understands what is going on. Having said that, I think there are practical applications. Suppose you were unaware of this result, and thought a true RE could validate your input? A more knowledgeable attacker might be able to craft an input that exploits the inherent limitations of your validator. Also in practice, attempting to write a true RE to parse a language that allows restricted recursion rapidly becomes complicated. It is the wrong tool for the job.