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->__(
e='this.form.submit();'>
<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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<div class='path'>path: <a href='/guix/log/?id=887dec8a51604408214d28290ce857451dcd7192'>root</a>/<a href='/guix/log/gnu?id=887dec8a51604408214d28290ce857451dcd7192'>gnu</a>/<a href='/guix/log/gnu/packages?id=887dec8a51604408214d28290ce857451dcd7192'>packages</a>/<a href='/guix/log/gnu/packages/patches?id=887dec8a51604408214d28290ce857451dcd7192'>patches</a>/<a href='/guix/log/gnu/packages/patches/gnome-boxes-add-guix-logo.patch?id=887dec8a51604408214d28290ce857451dcd7192'>gnome-boxes-add-guix-logo.patch</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/packages/patches/gnome-boxes-add-guix-logo.patch?id=887dec8a51604408214d28290ce857451dcd7192&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-11-27 13:43:54 +0100'>2021-11-27</span></td><td><a href='/guix/commit/gnu/packages/patches/gnome-boxes-add-guix-logo.patch?id=3466c055e66c2aa0dd8cbeb52a11701e1928a373'>gnu: gnome-boxes: Add Guix logo support.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/patches/gnome-boxes-add-guix-logo.patch: New patch.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/gnome.scm (gnome-boxes): Use it.
</span></span></td><td>Mathieu Othacehe</td></tr>