>>Setting `$=` to something truthy causes all string operations to become case-insensitive. This and other magic globals from perl are mind blowing.

>Perlisms.

They're incomplete Perlisms that's the real flaw because in perl these special variables are dynamically scoped.

NB. $= does something completely different in perl. I don't know of any perl special variable that replicates what Ruby's $= does.