The question is if you can understand the solution if it's complex.

Just like the regex for valid email addresses, it may be correct but it's hard to understand it.

I see it more as a tool for doing the tedious but simple work, if it's getting complex you get a hard time checking the correctness of the result.

Casual reminder what you shouldn't try to parse email addresses for a validity with regex, besides checking for '@' aaaaaaaand maybe for '@\w+?\.\w+?' if you are sure the code would only face the globally addressable addresses.

It is good at that and you can only paste so much data into the UI, so usually go this route for complex one liners.