Yet there's almost no real discussion of how to use the standard library here, and a lot of talking about example code that's mostly useless (seriously - why is biorhythm pseudoscience #2, and how is displaying a calendar on the CLI going to help me...?)
I agree with the top post - I have a very different idea about what "built-in" means than the author of this article.
And that's fine. But that topic in the article is not Date/OptionParser/GetOptLong - it's
"This week I'm sharp-as-a-tack, and slow and sad as a sack. Here's to next week!"
and I don't see any value add above linking to examples (not built-ins).
Ex - why not explore OptionParser (the actual built-in!) - and compare to ARGV, or contrast with gets.chomp. Or explain how similar the concept is to something like Yargs from the node side.
Also, as a personal aside - I don't really see a bunch of custom formatted printf statements with no attempt at explanation a very good example at all.
All of the examples given use only the standard lib, afaict.