http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21001

From 34163794a58b5bd91c5d6bd9adf5437571c7a479 Mon Sep 17 00:00:00 2001
From: Pavel Raiskup <praiskup@redhat.com>
Date: Tue, 7 Jul 2015 10:54:24 +0200
Subject: [PATCH] bin/automake: escape '{' in regexp pattern

Based on perlre(1) documentation:
.. in Perl v5.26, literal uses of a curly bracket will be required
to be escaped, say by preceding them with a backslash ("\{" ) or
enclosing them within square brackets ("[{]") ..

References:
https://bugzilla.redhat.com/1239379

* bin/automake.in (substitute_ac_subst_variables): Escape the
occurrence of '{' character.
--- a/automake.in
+++ b/automake.in
@@ -3898,7 +3898,7 @@ sub substitute_ac_subst_variables_worker
 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;
 }
 
-- 
2.1.0