Expressions consist of operands (numbers, strings,  constants,  variables,
  functions, or array elements) separated by:

   o  Arithmetic operators (+, -, *, /, ^, and **)
   o  String concatenation operator (+)
   o  Relational operators (=, <, >, <= or =>, >= or =>, <> or ><, and ==)
   o  Logical operators (NOT, AND, OR, XOR, EQV, and IMP)