Keys

Distinct identity labels. Keys are special labels that can never match any other value than itself.

foo .= `foo
`email@domain.com

They use ` as a prefix and any non-space codepoint after is part of the key's label. They are first-class objects and can be passed around with subroutines. Keys can even be used as map labels.

What are they for?

They are useful for skipping string comparisons in some kinds of programming patterns or hiding certain functionality to be only accessible by someone with the key.