if you dig in Pod::HTML, you will see that it opens another handle to access STDOUT behind your back and that breaks you tie. So you are probably better of to do:

my $temp = `pod2html $file`;
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Relevant extract from Pod::HTML

  $htmlfile = $opt_outfile  if defined $opt_outfile;
    ...
   $htmlfile = "-" unless $htmlfile;    # stdout
     ...
 # open the output file
    print STDERR ">$htmlfile";
    open(HTML, ">$htmlfile")
        || die "$0: cannot open $htmlfile file for output: $!\n";
[download]

-- stefp