Ruby lib/irb/easter-egg.rb

A tangent, but: I've read and written a lot of Ruby—except never much of the stdlib, for some reason—and I've literally never seen anyone use the `private` pseudo-keyword in the Java-esque way it's used here (`private def foo...` on the same line), to the point that I didn't even realize that that was possible.

I've always only seen these usages:

• `private` on its own line with surrounding whitespace, treated as a section-break in the class, where it has a "mode-switch for all that follows" effect similar to `private:` in C++.

• `private :foo` on a separate line after `def foo...`, where it's just acting as a standalone call to one of Class's "builder" DSL methods, like an `attr_reader` call.

• `private\ndef foo` (rare), as if `private` were some Java-like annotation modifying just the following method (though this is really just the first mode-switching kind, and later methods will need a `public\n` "annotation" to go back.)

Why is that? It seems startlingly obvious, once you see it done, that `private def ...` is the idiomatic way to use it. (After all, they bothered to make `def` return the symbolic name of the function you defined, just so you could chain it into class-builder-methods like this.)

Here's a one liner:

    ruby -r irb -e 'IRB.send(:easter_egg)'

And in Docker you get a static image, but sometimes, randomly you get the dynamic one...

    docker run --rm -it ruby:2.7.1-alpine ruby -r irb -e 'IRB.send(:easter_egg)'

I stumbled onto this when looking at the ruby source code, anyone know how to trigger it?