The operator with the highest precedence in an expression is
    evaluated first. Following this, the next highest operator
    precedence is evaluated, and so on. Operators with the same
    precedence are evaluated from left to right, as they appear in
    the expression.

       Operator Precedence Description

       +        5         String concatenation
       -        5         String reduction
       .EQS.    4         String equal
       .GES.    4         String greater than or equal
       .GTS.    4         String greater than
       .LES.    4         String less than or equal
       .LTS.    4         String less than
       .NES.    4         String not equal