cfer | Ruby DSL for automating infrastructure using AWS | AWS library

I initially posted this as an answer to this question earlier regarding Empty CGI.REDIRECT_URL on ColdFusion 2016. After thinking about it, I thought better of it since technically didn't answer the OP's question. Instead I decided to make it into a separate question, even though it's more of a commentary than a question. While this technically might not meet the full requirements of a Minimal, Complete, and Verifiable example and people might ding me with downvotes, I decided it was worth it anyway in the hope that it will become easier to find for future CFers who might encounter this. Thus preventing them from banging their head against the wall regarding this peculiar behavior of the CGI struct/scope.

With that said, the CGI struct/scope has some undocumented inconsistent behavior from other structs/scopes. Note that I personally take no credit for this discovery since I happened across this some time ago upon reading Ben Nadel's blog post on this. So all the information I'm posting here is already detailed there, but I wanted to write a nice summary here on SO.

Undocumented behavior 1 - Unlike other structures, if a CGI struct key doesn't exist, then it won't throw an error when referencing it.

In the OP's original question, he was wondering why cgi.REDIRECT_URL existed but was empty. As he eventually found out, it never actually existed. As a separate example you can execute this line of code without throwing an error. Not what you'd expect, huh?