use Win32::OLE::Variant;
# ...
my $filename = Variant(VT_BSTR|VT_BYREF, 0);
$XRawfile->GetFileName($filename);
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More details can be found near the bottom of Win32::OLE::Variant's POD.

--
You said you wanted to be around when I made a mistake; well, this could be it, sweetheart.