diff -ruN autoconf-2.13.orig/autoscan.pl autoconf-2.13/autoscan.pl
--- autoconf-2.13.orig/autoscan.pl	1999-01-05 14:28:42.000000000 +0100
+++ autoconf-2.13/autoscan.pl	2018-12-22 19:55:10.986732296 +0100
@@ -232,7 +232,7 @@
 	# Strip out comments and variable references.
 	s/#.*//;
 	s/\$\([^\)]*\)//g;
-	s/\${[^\}]*}//g;
+	s/\$\{[^\}]*}//g;
 	s/@[^@]*@//g;
 
 	# Variable assignments.