Fix a deprecation warning with newer Perl that breaks some tests.

--- a/tp/Texinfo/Parser.pm
+++ b/tp/Texinfo/Parser.pm
@@ -5438,12 +5438,12 @@
     }
   } elsif ($command eq 'clickstyle') {
     # REMACRO
-    if ($line =~ /^\s+@([[:alnum:]][[:alnum:]\-]*)({})?\s*/) {
+    if ($line =~ /^\s+@([[:alnum:]][[:alnum:]\-]*)(\{})?\s*/) {
       $args = ['@'.$1];
       $self->{'clickstyle'} = $1
         unless(_ignore_global_commands($self));
       $remaining = $line;
-      $remaining =~ s/^\s+@([[:alnum:]][[:alnum:]\-]*)({})?\s*(\@(c|comment)((\@|\s+).*)?)?//;
+      $remaining =~ s/^\s+@([[:alnum:]][[:alnum:]\-]*)(\{})?\s*(\@(c|comment)((\@|\s+).*)?)?//;
       $has_comment = 1 if (defined($4));
     } else {
       $self->line_error (sprintf($self->__(
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<div class='path'>path: <a href='/guix/log/?id=eb169d36e5c8f3c15b7716310c76829451a71fcd'>root</a>/<a href='/guix/log/gnu?id=eb169d36e5c8f3c15b7716310c76829451a71fcd'>gnu</a>/<a href='/guix/log/gnu/services?id=eb169d36e5c8f3c15b7716310c76829451a71fcd'>services</a>/<a href='/guix/log/gnu/services/sysctl.scm?id=eb169d36e5c8f3c15b7716310c76829451a71fcd'>sysctl.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/services/sysctl.scm?id=eb169d36e5c8f3c15b7716310c76829451a71fcd&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-04-29 18:07:16 +0200'>2022-04-29</span></td><td><a href='/guix/commit/gnu/services/sysctl.scm?id=9d7248cd87fbda8c717341a8092780782bef0820'>services: Add missing 'description' fields.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/databases.scm (postgresql-service-type)[description]: New field.
(memcached-service-type)[description]: New field.
(mysql-service-type)[description]: New field.
(redis-service-type)[description]: New field.
* gnu/services/desktop.scm (geoclue-service-type)[description]: New
field.
(udisks-service-type)[description]: New field.
(elogind-service-type)[description]: New field.
(account-service-type)[description]: New field.
* gnu/services/kerberos.scm (krb5-service-type)[description]: New field.
(pam-krb5-service-type)[description]: New field.
* gnu/services/lirc.scm (lirc-service-type)[description]: New field.
* gnu/services/mail.scm (dovecot-service-type)[description]: New field.
(opensmtpd-service-type)[description]: New field.
(mail-aliases-service-type)[description]: New field.
(exim-service-type)[description]: New field.
* gnu/services/monitoring.scm (zabbix-server-service-type)[description]:
New field.
(zabbix-agent-service-type)[description]: New field.
* gnu/services/nfs.scm (rpcbind-service-type)[description]: New field.
(pipefs-service-type)[description]: New field.
(gss-service-type)[description]: New field.
(idmap-service-type)[description]: New field.
* gnu/services/spice.scm (spice-vdagent-service-type)[description]: New field.
* gnu/services/sysctl.scm (sysctl-service-type)[description]: New field.
* gnu/services/virtualization.scm (libvirt-service-type)[description]:
New field.
(virtlog-service-type)[description]: New field.
* gnu/services/vpn.scm (openvpn-server-service-type)[description]: New field.
(openvpn-client-service-type)[description]: New field.
(wireguard-service-type)[description]: New field.
* gnu/services/web.scm (httpd-service-type)[description]: New field.
(fcgiwrap-service-type)[description]: New field.
(agate-service-type)[description]: New field.
[name]: Fix.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-03-31 15:36:49 +0200'>2021-03-31</span></td><td><a href='/guix/commit/gnu/services/sysctl.scm?id=4f547c50f9bc478fd7c8bb9d481e2e376b969e8a'>services: sysctl: Export &lt;sysctl-configuration&gt; record field accessors.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/sysctl.scm (sysctl-configuration-sysctl)
(sysctl-configuration-settings): Export.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>muradm</td></tr>
<tr><td><span title='2021-03-18 12:17:33 +0100'>2021-03-18</span></td><td><a href='/guix/commit/gnu/services/sysctl.scm?id=898489f48e436e45e86e1ba0fcdb6df5cd5a051a'>services: Enable "protected hardlinks" and "protected symlinks" by default.</a><span class='msg-avail'>...<span class='msg-tooltip'>References:

https://sysctl-explorer.net/fs/protected_hardlinks/
https://sysctl-explorer.net/fs/protected_symlinks/

* gnu/services/sysctl.scm (%default-sysctl-settings): New public variable.
(&lt;sysctl-configuration&gt;): Use %default-sysctl-settings as the default value.
* gnu/services/base.scm (%base-services): Add sysctl-service-type.
* doc/guix.texi (Miscellaneous Services): Document the new defaults.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Leo Famulari</td></tr>