From the documentation on the old Spreadsheet::WriteExcel module 
MODIFYING AND REWRITING EXCEL FILES 

An Excel file is a binary file within a binary file. It contains sever
+al interlinked checksums and changing even one byte can cause it to b
+ecome corrupted.

As such you cannot simply append or update an Excel file. The only way
+ to achieve this is to read the entire file into memory, make the req
+uired changes or additions and then write the file out again.

You can read and rewrite an Excel file using the Spreadsheet::ParseExc
+el::SaveParser module which is a wrapper around Spreadsheet::ParseExc
+el and Spreadsheet::WriteExcel. It is part of the Spreadsheet::ParseE
+xcel package: http://search.cpan.org/search?dist=Spreadsheet-ParseExc
+el.

However, you can only rewrite the features that Spreadsheet::WriteExce
+l supports so macros, graphs and some other features in the original 
+Excel file will be lost. Also, formulas aren't rewritten, only the re
+sult of a formula is written.

[download]
The xlsx format is somewhat better documented, but the problem appears to remain.

print "Good ",qw(night morning afternoon evening)[(localtime)[2]/6]," fellow monks."

In reply to Re: Excel how to open existing worksheet by Utilitarian
in thread Excel how to open existing worksheet by AtlasFlame

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