These methods usually return string variants. Something like this should work: -

my ($strUser, $strDomain) = (
    Variant(VT_BSTR|VT_BYREF, '<undef>'), 
    Variant(VT_BSTR|VT_BYREF, '<undef>')
);
$objWMIProcess->GetOwner($strUser, $strDomain);
print 'Owner: ' . $strDomain->Value . '\\' . $strUser->Value, "\n";
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