I was able find/replace text in the body of the Doc file, thanks to internet, but I am not able to find/replace text in the header/footer.

 $word = Win32::OLE-> GetActiveObject('Word.Application')
    || Win32::OLE-> new('Word.Application','Quit');

my $Wordsections = $word->{Sections};

my $sections = $doc->{Sections};
my $n_sections = $sections->{Count};

for my $s ( 1 .. $n_sections ) {

   my $section = $sections->Item($s);

   my $headers = $section->{Headers};
   my $n_headers = $headers->{Count};

   for my $h ( 1 .. $n_headers ) {
      my $header = $headers->Item($h);
      print $header->{Range}->{Text}, "\n";
      #my $headerRange=$headers->Range("wdHeaderFooterIndex")->InRange
+="TRUE";
      $Wordsections->Find->ClearFormatting;
      $Wordsections->Find->{Text} = 'SECRET';
      $Wordsections->Find->Replacement->{Text} = "NOFORN";
      $Wordsections->Find->Execute({Replace => wdReplaceAll});
      
   }
   
   my $footers = $section->{Footers};
   my $n_footers = $footers->{Count};
   
   for my $f ( 1 .. $n_footers ) {
      my $footer = $footers->Item($f);
      print $footer->{Range}->{Text}, "\n";
     }
}
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