Historic
Executes a code block by evaluating an entity according to its current value as well as all previous values.

Exceptional
Designates an abnormal flow of program execution and guarantees that it will never be handled as an error.

Flee
A branching construct that moves flow control from the current instruction to a stray position in the program.

Maybe
Allows for possible, but not guaranteed, execution of code blocks.

Never
Guarantees that a block of code will never be executed. This is similar to block quotes in other languages, except that “never” blocks are not removed during compilation.

Potential
Evaluates an entity only according to as yet unrealized possibility.