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.
The result_expression has access to all the variables (name, name2, …) defined in the VAR statement(s) before RETURN.