

          crange string firstExpr lastExpr
               Returns a range of characters from string starting at
               the character indexed by the expression firstExpr
               (zero-based) until the character indexed by the
               expression lastExpr.  The special keyword end may be
               specified for last to indicate that the remainder of
               the string is to be extracted.  This command is a
               shortcut for:

                   string range string [expr firstExpr] [expr lastExpr]
