The readability isn't so bad if you let yourself allocate as much time and mental effort to understanding the one-line regex as you would use to understand the

The readability isn't so bad if you let yourself allocate as much time and mental effort to understanding the one-line regex as you would use to understand the 100 line string-processing function that it replaces. And the brevity makes regexes handy on the command line and in single-line input fields in text editor search functions. I do prefer using parser combinators for more complex tasks.