Section 8,8: Substrings

 A character substring is a contiguous segment of a character
 variable, character array element, or character field reference.
 It has one of the following forms:

    v([e1]:[e2])  OR  a(s[,s]...)([e1]:[e2]) 

    v    Is a character variable name
    a    Is a character array name
    s    Is a subscript expression
    e1   Is a numeric expression specifying the leftmost
         character position of the substring
    e2   Is a numeric expression specifying the rightmost
         character position of the substring
 NOTE:
   1 .LE. e1 .LE. e2 .LE. length-of-v must hold true