I looked more carefully at the Net::Amazon change document. I realize that the are referring to ECS3 and 4 as AWS3 and 4.

From the change document.-- http://search.cpan.org/src/BOUMENOT/Net-Amazon-0.46/Changes

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0.36 (01/09/2007) (cb) Christopher Boumenot is taking over has maintainer of Net::Amazon. (cb) Update the library to use AWS4 from AWS3. The changes involved are quite deep. While I have strived to keep interfaces the same that was not always possible. I am sure there are still bugs to be had that need to be fixed. -----------------

The last update to the module in 11/16/07

I will update my copy of the module, test it to see if there are any interface changes, and modify my code if needed.