Perl 5.22 complaining about:
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/\${ <-- HERE ([^ \t=:+{}]+)}/ at
/builds/userland/automake/automake-1.11.2/build/i386/bin/automake line 393

Should send this upstream.

--- automake-1.11.2/automake.in_orig	2016-03-16 10:45:17.884191948 -0700
+++ automake-1.11.2/automake.in	2016-03-16 10:46:39.539918802 -0700
@@ -4150,7 +4150,7 @@
 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;
 }