I haven't read the article completely, but I've enjoyed what I've read so far. I'd like to follow along in more detail with a perl interpreter. I'd love to see an entire book that completely tears down the entire interrupter from the perspective of within.
I purchased Ruby Under a Microscope, but I was kind of put off by the similar issues other commentators are having, that it appears to be a basic introduction to how to write Ruby, but that is just how the task has to be approached (based off your existing assumptions and test to see if they hold up). But when the task is complete, you have knowledge on a better way to write Ruby, by accounting for all the exceptions that you can't "see" in the source code, due to leaky abstractions.
I purchased Ruby Under a Microscope, but I was kind of put off by the similar issues other commentators are having, that it appears to be a basic introduction to how to write Ruby, but that is just how the task has to be approached (based off your existing assumptions and test to see if they hold up). But when the task is complete, you have knowledge on a better way to write Ruby, by accounting for all the exceptions that you can't "see" in the source code, due to leaky abstractions.