Dist::Zilla builds distributions of code to be uploaded to the CPAN. In this respect, it is like ExtUtils::MakeMaker, Module::Build, or Module::Install. Unlike those tools, however, it is not also a system for installing code that has been downloaded from the CPAN. Since it's only run by authors, and is meant to be run on a repository checkout rather than on published, released code, it can do much more than those tools, and is free to make much more ludicrous demands in terms of prerequisites.
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