I got, thanks for all! The problem was that Vendor::Amazon had:

use base Vendor::Base;
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one thing I did but couldn't associate with was:

use strict;
use base Vendor::Base;
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then I realized that if strict goes after, no problem. Later I figured all out: base is the module and Vendor::Base is the parameter, so quotes are necessary around Vendor::Base. with strict after or without strict, no problem without quote.

That's it. Thanks again.