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->__(
>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
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<input type='hidden' name='id' value='95f6e6dad80aa198b5b8d02851050bcfe0928c26'/><input type='hidden' name='showmsg' value='1'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
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<div class='path'>path: <a href='/guix/log/?id=95f6e6dad80aa198b5b8d02851050bcfe0928c26&amp;showmsg=1'>root</a>/<a href='/guix/log/etc?id=95f6e6dad80aa198b5b8d02851050bcfe0928c26&amp;showmsg=1'>etc</a>/<a href='/guix/log/etc/snippets?id=95f6e6dad80aa198b5b8d02851050bcfe0928c26&amp;showmsg=1'>snippets</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/etc/snippets?id=95f6e6dad80aa198b5b8d02851050bcfe0928c26'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2019-05-09 00:22:37 -0400'>2019-05-09</span></td><td class='logsubject'><a href='/guix/commit/etc/snippets?id=4ac69ea10f54384ac893313ef738e5ad554ac328'>Add (guix bzr-download).</a></td><td>Maxim Cournoyer</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* guix/bzr-download.scm, guix/build/bzr.scm,
etc/snippets/scheme-mode/guix-bzr-reference: New files.
* Makefile.am (MODULES): Add them.
* etc/snippets/scheme-mode/guix-origin: Add "bzr-fetch" to the origin choices.


</td></tr>
<tr class='logheader'><td><span title='2019-03-26 14:18:12 +0100'>2019-03-26</span></td><td class='logsubject'><a href='/guix/commit/etc/snippets?id=6994e6743603ab73cc32d32786a55672f4fa46f0'>etc: Add "rename" snippet.</a></td><td>Pierre Neidhardt</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* etc/snippets/text-mode/guix-commit-message-rename-package: New file.


</td></tr>