Aを文字列の配列A$にして実行すると、 ["0","1","2","3","4","5","6","7","8","9"]が、 ["0","0","0","0","0","0","0","0","0","0"]になります。 これは、文字列が参照型の面もあるので、 A$[1]=A$[0] A$[2]=A$[1] … という感じなり、全て0になる理由がわかります。