What "existing solution"? And why isn't length_in_grapheme_clusters() sufficient?
Once again, it's obvious you're making some point, the thrust of which is undoubtedly that I'm wrong about something I wrote, but you're making it too laconically for me to get it. I have no idea what you're saying.
By the way, the version of length_in_grapheme_clusters() I used in my Perl script is attributable to Tom Christiansen. I borrowed it from a PerlMonks post of his. To me, it's better because it makes the operation plainly clear. Your version is tricky and obfuscated, and seemingly weirdly dependent on context. To be honest, I don't understand how it works. To learn how it works, I'd have to read the Perl documentation.