r-char ::= '{any member of the source character set, except a right parenthesis ")" followed
by}' '{the initial d-char-sequence (which may be empty) followed by a double quote
".}'
d-char ::= '{any member of the basic source character set except:}' '{space, the left
parenthesis "(", the right parenthesis ")", the backslash "\", and the control characters}'
'{representing horizontal tab, vertical tab, form feed, and newline.}'