When you specify an expression, DCL evaluates values based on
    the operations specified in the expression. The values can be
    integers or character strings.

    Some expression operators are conventional mathematical
    symbols, for example, plus sign (+). Others specify logical
    and comparison operations, and consist of letters preceded and
    followed by periods; for example, .EQS. Operators are assigned a
    precedence that determines their order of evaluation. You can use
    parentheses to override this order.

    For additional information on specifying expressions, refer to
    the VSI OpenVMS User's Manual.