Spreadsheet::WriteExcel is used only for writing Excel files. It understands the Excel format but does not have a spreadsheet display engine in it. To actually display a spreadsheet you need Microsoft Excel itself or a compatible application such as Gnumeric or OpenOffice. Each of these has its own API and different Perl bindings for them.

Update: It appears that OpenOffice does not have an officially supported API binding for Perl, though one is under development here.