If the value of the argument is greater than the number of clauses, nothing is printed.

However, if the last clause separator is ~:; instead of ~;, then the last clause serves as a default clause.

and then use it like this:

Note that the control string actually contains two ~[~] directives—both of which use to select the clause to use. The first consumes between zero and two arguments, while the second consumes one more, if available. **FORMAT** will silently ignore any arguments not consumed while processing the control string.

Note that either clause can be empty, but the directive must contain a ~;.

Finally, with an at-sign modifier, the directive can have only one clause. The directive consumes one argument and, if it’s non-**NIL**, processes the clause after backing up to make the argument available to be consumed again.