this one won't work so well though ☹

I tried to use a subshell to try to convert, to make it more robust
against invalid utf-8, but that didn't work out

check.t

@@ -1,4 +1,4 @@
-# $MirOS: src/bin/mksh/check.t,v 1.181 2008/04/20 00:24:25 tg Exp $
+# $MirOS: src/bin/mksh/check.t,v 1.182 2008/04/20 00:28:30 tg Exp $
 # $OpenBSD: bksl-nl.t,v 1.2 2001/01/28 23:04:56 niklas Exp $
 # $OpenBSD: history.t,v 1.5 2001/01/28 23:04:56 niklas Exp $
 # $OpenBSD: read.t,v 1.3 2003/03/10 03:48:16 david Exp $
@@ -4822,13 +4822,12 @@ stdin:
 		while IFS= read -r line; do
 			line=$line$nl
 			while [[ -n $line ]]; do
-				(( hv = 1#${line::1} & 0xFF ))
-				if (( hv < 0xC2 )); then
-					n=1
-				elif (( hv < 0xE0 )); then
+				if (integer x=1#${line::3}) 2>&-; then
+					n=3
+				elif (integer x=1#${line::2}) 2>&-; then
 					n=2
 				else
-					n=3
+					n=1
 				fi
 				wc=1#${line::n}
 				if (( (wc < 32) || \