This first edition was written for Lua 5.0. While still largely relevant for Lua 5.1, there are some differences.
The second edition targets Lua 5.1 and is available at Amazon and as an e-book.
By buying the book, you also help to support the Lua project.

Part I. The Language Chapter 3. Expressions

3 – Expressions

Expressions denote values. Expressions in Lua include the numeric constants and string literals, variables, unary and binary operations, and function calls. Expressions can be also the unconventional function definitions and table constructors.