--- automake-1.12.6/automake.in.orig	2016-02-28 09:52:53.000000000 +1100
+++ automake-1.12.6/automake.in	2016-02-28 09:53:00.000000000 +1100
@@ -4030,7 +4030,7 @@
 sub substitute_ac_subst_variables ($)
 {
   my ($text) = @_;
-  $text =~ s/\${([^ \t=:+{}]+)}/&substitute_ac_subst_variables_worker ($1)/ge;
+  $text =~ s/\$\{([^ \t=:+{}]+)}/&substitute_ac_subst_variables_worker ($1)/ge;
   return $text;
 }