After some playing with the code, I think I figured out what is going on. As your reference, open the Camel book, 3rd ed, to page 484.

The thing with the INIT block is that it is executed _after_ compilation but _before_ the rest of the program is run. Another way to say it is that code in INIT block "runs just before the runtime." Then, if some code that uses INIT blocks is eval'ed, this means that the point in time _before_ runtime has passed, and INIT block does not execute.

Fine, that answered my first question. Another problem that within eval'ed INIT block,

sub A::B::c { ... }
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works fine. After thinking about this, it begins to make sense to me. A subroutine definition is _not_ code, but a language construct. While something like *{xyz} = sub {}; is a statement, sub abc {} is not!

Please correct me if I'm wrong, but I think I figured it out.