I decided it was time I wrote a Computer Science EAI exercise and that is what I have just finished doing. I have made it publicly available as one of my Internationalised Programming Challenges ➜ jsfiddle.net/coas/2uLhcfef<http://jsfiddle.net/coas/2uLhcfef> My reasoning behind this exercise includes: ① Raising awareness of EAI ② Encouraging students to think about what constraints they would impose on EAI address registrations ③ Encouraging students to think beyond ASCII When I finished writing this exercise I was thinking this is too simple. But, it is only simple if one has understanding of Unicode and Unicode aware regular expression engines like PCRE2. Actually, just a couple of days ago, one of my project students said to me: "If not for you, I would know nothing about Unicode" André Schappo