Win32::OLE won't work on Solaris I believe.Spreadsheet::WriteExcel will write the files but it isn't able to write to an existing Excel file.

Perhaps re-think your design on this one. If all you need from the Solaris server is the results of a db query. Then connect to it via DBI and put the results into the Excel sheet via Win32::OLE on the Windows machine. This all assumes you can connect via DBI to your database.