From <https://lists.gnu.org/archive/html/automake-patches/2015-07/msg00000.html>.
See also <http://bugs.gnu.org/22372>.

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.
---
 bin/automake.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bin/automake.in b/bin/automake.in
index 0c29184..c294ced 100644
--- a/bin/automake.in
+++ b/bin/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;
 }
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<tr><td><span title='2021-12-13 17:48:25 +0100'>2021-12-13</span></td><td><a href='/guix/commit/gnu/packages/efi.scm?id=8394619baceb118df92e355377fd543bb1aa501a'>gnu: Simplify package inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>This commit was obtained by running:

  ./pre-inst-env guix style

without any additional argument.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-03-27 22:47:02 +0100'>2021-03-27</span></td><td><a href='/guix/commit/gnu/packages/efi.scm?id=02a2c7e53cc0070233c31f52600bec5e6a0d7c72'>gnu: gnu-efi: Update to 3.0.13.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/efi.scm (gnu-efi): Update to 3.0.13.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-01-14 17:18:16 +0100'>2021-01-14</span></td><td><a href='/guix/commit/gnu/packages/efi.scm?id=f79f41e2403e69e4ae5c57e2a5cbd348d8677a98'>gnu: efi-analyzer: Rename with a hyphen instead of an underscore.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/efi.scm (efi_analyzer): Rename to...
(efi-analyzer): ... this.
(efi_analyzer): Redefine as a deprecated alias.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-01-12 22:51:35 +0100'>2021-01-12</span></td><td><a href='/guix/commit/gnu/packages/efi.scm?id=4de576e9b26ea3e634c1cd819600851ee3a5c6d6'>gnu: Fix comment typo.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/efi.scm: Purge spurious space.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-01-12 22:08:33 +0100'>2021-01-12</span></td><td><a href='/guix/commit/gnu/packages/efi.scm?id=373f808df229c12101301b766bd1810836b98481'>gnu: Add efi_analyzer.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/engineering.scm (efi_analyzer): New variable.

Signed-off-by: Tobias Geerinckx-Rice &lt;me@tobias.gr&gt;
</span></span></td><td>Vincent Legoll</td></tr>