R4RS 6.7  (string<? string1 string2)      ==>  boolean
          (string>? string1 string2)      ==>  boolean
          (string<=? string1 string2)     ==>  boolean
          (string>=? string1 string2)     ==>  boolean
          (string-ci<? string1 string2)   ==>  boolean
          (string-ci>? string1 string2)   ==>  boolean
          (string-ci<=? string1 string2)  ==>  boolean
          (string-ci>=? string1 string2)  ==>  boolean

These procedures are the lexicographic extensions to strings of
the corresponding orderings on characters. For example, STRING<?
is the lexicographic ordering on strings induced by the ordering
CHAR<? on characters. If two strings differ in length but are
the same up to the length of the shorter string, the shorter
string is considered to be lexicographically less than the
longer string.

Implementations may generalize these and the STRING=? and
STRING-CI=? procedures to take more than two arguments, as with
the corresponding numerical predicates.

The S9fES versions of these procedures do accept more than two
arguments.
