I think Win32::OLE - Excel chart location might help you with your problem basically you have to specify a location for the charts

Said that I'm going to take the opportunity to give you an advice, if I can stay away from Platform specific solutions like Win32::OLE I would because if you ever want to migrate to another platform you'll have a big headache ( don't think you'd never have to ) and probably niether API docs are easy to find for close source apps like Excel nor contact the developers in case something goes wrong.

There is a fantastic module in CPAN Spreasheet::WriteExcel with a lot of features including charts. Bonus: You'll get much more support here (multi-platform) and you'll probably save hundred MBs as you are not instantiating an Excel.Application :D

Finally I'd recommend you start including use strict; and use warnings; in your code to help you diagnosing problems