diff -Naur autoconf-2.69.orig/bin/autoscan.in autoconf-2.69/bin/autoscan.in
--- autoconf-2.69.orig/bin/autoscan.in	2012-04-24 22:37:26.000000000 -0400
+++ autoconf-2.69/bin/autoscan.in	2020-05-31 19:40:31.728268832 -0400
@@ -358,7 +358,7 @@
     {
       # Strip out comments and variable references.
       s/#.*//;
-      s/\${[^\}]*}//g;
+      s/\$\{[^\}]*}//g;
       s/@[^@]*@//g;
 
       # Tokens in the code.