[croes]

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.

[justsomehnguy]

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.