An Excel file is a collection of binary files within a binary file. It contains several interlinked checksums and changing even one byte can cause it to become corrupted.

As such it isn't possible to template a binary Excel file in the same way that you would template a text file.

Hence the route that Excel::Template and Spreadsheet::WriteExcel::FromXML take where the tempate file is text or XML based and the backend uses Spreadsheet::WriteExcel to create the Excel binary file.

The newer xlsx Excel files from Excel 2007 onwards are XML files contained in a zip file and are more suitable for TT style templating.

As an aside I am working on an xlsx writer module that will eventually read and rewrite files as well so that it will be possible to use an existing file as a template (although not in the TT sense). However, that work is still at an early stage.

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John.