A *metaterm* is a literal that represents a term. You can think of it as a fancy sort of string. Metaterms are created with the at symbol (
Consider a case where we need to know if a term is a variable. We might have an operator like
is_variable that takes a single argument and evaluates to
true when the argument is a variable, and to
false when it is not. We might use that in a lambda, but if we do, we have to *defer evaluation* until we are ready.
Here this will *immediately* be rewritten to