bug fix on operand operation for left().

tests/dump.txt

@@ -6,9 +6,10 @@ complete=[ABCD;tohex]
 division=[1.666666666667]
 divisor=[8]
 error=[64]
+exprnumbers=[0123456789]
 include=[yes]
 ix=[1]
-lefty=[]
+lefty=[01234]
 modified1=[ABCD]
 multiplication=[15]
 nested=[64]