Editor's note: No, don't do this.
Regular expressions get a bad rap -- a regex is a powerful tool, good for some jobs and terrible for others.
I would be pretty interested in a puzzle game with gradually-escalating regex complexity (especially using the search text for storytelling). But Copy Editor takes an early turn in ... another direction.
In this level, the search text has gendered pronouns that need to be gender-swapped. So how do you change "His" to "Her" and "Her" to "His" without undoing yourself? The real-life answer is don't use regex. It's the wrong tool for this job, and this problem shouldn't be in a regex game at all.
Copy Editor teaches you to look for specific instances, instead of general patterns, which is the wrong way to use regular expressions.
Like, at this point, why not re-type the text?
I know I'm digressing into computer science philosophy here, and these guys are just trying to make a game. Okay. I only hope that I don't have to work with a junior programmer who learns to abuse regexes from Copy Editor.
Progress: I think this is in the demo's second level.