Uh, no. That's a bad plan. You're assuming that Microsoft wants to keep anything in their applications similar from version to version. Microsoft has a vested interest in not maintaining outside compatibility between versions. That way, you have to use their software.

Better is to use the modules whose maintainers are willing to handle this issue. If you want, write a XLS -> XML converter, using Spreadsheet::WriteExcel and your favorite XML writer. At least, you'll know that the DTD won't change just cause the version of Excel you saved the file in changed.

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We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.

Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.