The VAR keyword introduces variables in an expression.
The syntax after VAR defines a variable, which can be consumed in following VAR statements or within the mandatory RETURN statement following the declaration of one or more variables.
If VAR is used in the DEFINE section of an EVALUATE statement, it can be used in any expression of the statement and the RETURN keyword cannot be used.

VAR <name> = <expression>
[VAR <name2> = <expression2> [...]]
RETURN <result_expression>

The expression is evaluated only once and assigned to the name in the scope of the expression where the VAR/RETURN expression is used.
The expression2 has access to name.
A variable nameN is visible in all the expressionN+1 of following variables defined within the same VAR/RETURN statement.
If an expression contains the definition of other variables in nested VAR/RETURN statements, the nested variables are not visible outside of the scope of expression. Indeed, the result_expression has access to all the variables (name, name2, …) defined in the VAR statement(s) before RETURN in the same statement, but it does have access to variable defined in nested VAR/RETURN statements applied to assigned to variables.