Try the latest version of Spreadsheet::ParseExcel which has a parser error() method that may report some useful information:

    ...
    my $parser   = Spreadsheet::ParseExcel->new();
    my $workbook = $parser->parse('Book1.xls');

    if ( !defined $workbook ) {
        die $parser->error(), ".\n";
    }
    ...
[download]

It may be that you are trying to parse an encrypted file or an xlsx file.

That memory reduction technique is also included in the main documentation now.

--
John.