Module::Install::Deprecated are warnings and help for deprecated commands.
One of the nicest features of Module::Install is that as it improves, there is no need to take into account user compatibility, because users do not need to install Module::Install itself.
As a result, the Module::Install API changes at a faster rate than usual, and this results in deprecated commands.
Module::Install::Deprecated provides implementations of the deprecated commands, so that when an author is upgrading their Module::Install and they are using a deprecated command they will be told that the command has been deprecated, and what the author should use instead.
This extension should NEVER end up bundled into the distribution tarball.