Workaround for utf8::decode bug (sometimes utf8 chars were not decoded)

Remember the problem with toc.pl when the whole page was *sometimes* not
utf8-decoded? There were some thoughts that it might be associated with
memory files, and it is correct. Although I was not able to narrow it down
last time, now I did (simply because this problem appeared elsewhere).

If you look at $output variable after utf8::decode with Devel::Peek, you
will see two variants of flags. This one looks good:
   FLAGS = (PADMY,POK,pPOK,UTF8)
And this one is wrong:
   FLAGS = (PADMY,POK,pPOK)
This problem is weird because it works inconsistently. Most of the time
you will get correct output, but sometimes it will be broken.

Someone has to golf it down to something short in order to submit perl
bug report. This, however, does not look like a simple task.

Current workaround is as stupid as it looks like, but it works.
Somehow assigning it to another variable solves the problem (which, by the
way, is similar to solving other perl string-related problems).

modules/toc.pl

@@ -231,12 +231,15 @@ sub NewTocApplyRules {
   my ($html, $blocks, $flags);
   {
     local *STDOUT;
-    open(  STDOUT, '>', \$html) or die "Can't open memory file: $!";
+    my $html_unfixed;
+    open(  STDOUT, '>', \$html_unfixed) or die "Can't open memory file: $!";
     binmode STDOUT, ":encoding(UTF-8)";
     ($blocks, $flags) = OldTocApplyRules(@_);
     close  STDOUT;
     utf8::decode($blocks);
-    utf8::decode($html);
+    # do not delete!
+    $html = $html_unfixed; # this is a workarond for perl bug
+    utf8::decode($html);   # otherwise UTF8 characters are SOMETIMES not decoded.
   }
   # If there are at least two HTML headers on this page, insert a table of
   # contents.

wiki.pl

@@ -1251,8 +1251,9 @@ sub ToString {
   $sub_ref->();
   select $oldFH;
   close $outputFH;
-  utf8::decode($output);
-  return $output;
+  my $output_fixed = $output;  # do not delete!
+  utf8::decode($output_fixed); # this is a workarond for perl bug
+  return $output_fixed;        # otherwise UTF8 characters are SOMETIMES not decoded.
 }
 
 sub PageHtml {