if/unless


if (<cond>) {
    <statement1>;
    <statement2>;
} else {
    <statement3>;
    <statement4>;
}

Evaluate <statement1> and <statement2> if <cond> is true.
Otherwise, evaluate <statement3> and <statement4>.

The `else' part can be omitted.

`unless' works the same, but inverts the meaning of <cond>.