; 
 
   The string tokens identified by this routine are Fortran-style 
   quoted strings:  they start and end with quote characters.  In the 
   interior of any such token, any quote characters are represented 
   by doubled quote characters.  These rules imply that the number of 
   quote characters in a quoted string token is always even.  The end 
   of a quoted string token is located at the first even-numbered 
   quote character, counting from the initial quote character, that 
   is  not the first m