Perl script to Merge contents of 2 different excel files in a single excel file

All,

I have an excel sheet Excel1.xls that has some entries.
I have one more excel sheet Excel2.xls that has entries only in those cells which are blank in Excel1.xls

These may be in different workbooks. They are totally independent made by 2 different users.

I have placed them in a single folder in windows system.

Now I want to write a perl sheet to create a third sheet Result.xls that will contain contents of both these files.
That is it will have complete information present by using Excel1 and excel2.
How can I do this??

What is the max number of field of each ?