A learning aid for engines. Very small engine for a very small language. Implements the following:

Script: Expression Expression: A Expression B Expression C Expression D Expression A : "a" B : "b" C : "c" D : "d" 

A : "a"

Execution Step: Print "goose"

B : "b"

Execution Step: Print "duck"

C : "c"

Execution Step: Print "swan"

D : "d"

Execution Step: Print "finch"