1.1.1 * Let $x, y, z$ be non-zero real numbers. List the set of all possible values of the algebraic expression $\frac{x}{|x|}+\frac{y}{|y|}+\frac{z}{|z|}+$ $\frac{x y}{|x y|}+\frac{x y z}{|x y z|}$.
Parse: According to the number of negative numbers among $x$, $y$, and $z$ being $3, 2, 1, 0$, the corresponding values are $-3, -1, 1, 5$. The required set is $\{-3, -1, 1, 5\}$.