Except that the vast majority of those OCRs are just a series of letters. They all parse as "a variable name, that's it", and it's not even weird for that to be a valid line.

It's the kind of joke that doesn't teach you anything, rather than the kind that does.

I learned that:

    the Perl program “ Illegal division by zero at/tmp/quine.pl line 1. ”, when saved in theappropriate location, outputs “ Illegaldivision by zero at /tmp/quine.plline 1.”

I think there are a couple of neat examples there:

  lerzfijglpFiji-j

  -*?

plus I learned about the "unquoted string" feature that is the reason why the joke works

also, the writing is quite entertaining.

It's not so much a feature as how really old versions of Perl worked. Any program using strict doesn't allow it unless it's a known subroutine name, built-in or other symbol.

Except in certain cases because back-compat is complicated.