Other cases? Nobody on the internet seems to check for a return value for Close. http://cpansearch.perl.org/src/JDB/Win32-OLE-0.1709/t/6_event.t shows a way to check

printf "# Workbookcount: %d\n", $Excel->Workbooks->Count;
$Book->Close;
my $Count = $Excel->Workbooks->Count;
print "# Workbookcount: $Count\n";
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