Is $keyscore inside of the by_score subroutine the same as the one from your loop? At guess, I'd say it's not. Try putting the subroutine inline:

foreach $keyscore (sort { $totalscoreinv{$keyscore}{$b}<=>$totalscorei
+nv{$keyscore}{$a} } keys %totalscoreinv) {
   ...
}
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