Section 8,5,2: Character

 Character expressions consist of character elements and character
 operators.  Evaluation of a character expression yields a single
 value of character data type.  A character element may be a
 constant, variable, record element, array element, substring,
 expression (optionally enclosed in parentheses), or a function
 reference.

 A character expression has the form:

   character element[//character element]...

 The concatenation operator (//) is the only character operator.
 Concatenation is from left to right.