Variables and conditions.

VAR(VAR1, ... , VAR N) - Creates variables VAR1, ... VAR N if they don't exist.

VarName := Value - Assigns Value to variable VarName, for example \a:=4\

SET(VarName, Value) - Assigns Value to variable VarName.

IIF(Logical_expr, Value1, Value2) - Returns one of two values depending on the value of a logical expression. This function, also known as Immediate IF, evaluates a logical expression and then returns one of two expressions. If the logical expression evaluates to True, IIF( ) returns the first expression. If the logical expression evaluates to False, IIF( ) returns the second expression. 

Next topic: String functions