6.1.1 Constant Expressions

The simplest type of expression is the constant, which always has the same value. There are three types of constants: numeric, string, and regular expression.

Each is used in the appropriate context when you need a data value that isn’t going to change. Numeric constants can have different forms, but are internally stored in an identical manner.

Scalar Constants    Numeric and string constants.
Nondecimal-numbers    What are octal and hex numbers.
Regexp Constants    Regular Expression constants.