:) well I checked it, $header has the stuff, so a quick skim of the docs for "encod" ... arrive at https://metacpan.org/pod/distribution/OpenOffice-OODoc/OODoc.pod#odfDecodeText-ootext

# my $header = "\x{5D1}\x{5E1}\x{5F4}\x{5D3}";
# my $header = odfEncodeText( "\x{5D1}\x{5E1}\x{5F4}\x{5D3}" ); ## fai
+l
my $header = odfDecodeText( "\x{5D1}\x{5E1}\x{5F4}\x{5D3}" ); ## bingo
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This builds a file without complaining too much, but I can't open that file, my old version of openoffice 3.1 says its corrupt

update:

kind of related but you have no sheet to normalize Bug #110420 for OpenOffice-OODoc: suspect OpenOffice::OOdoc bug, please help

also related Bug #117523 for OpenOffice-OODoc: OODoc::XPath::inputTextConversion doesn't handle Perlstrings as input

So one step closer :)