--- clone
--- dup

    쥷ФƱƤĿ֤ޤclone 
    frozen tainted singleton-class ξޤƥԡޤ
    dup Ƥ򥳥ԡޤ

    ޤɤΥ᥽åɤǤ켫ΤΥԡϤޤ
    Ĥޤ(shallow)ץԡԤޤ

    :
        ary = ['string']
        p ary             #=> ["string"]
        copy = ary.dup
        p copy            #=> ["string"]

        ary[0][0...3] = ''
        p ary             #=> ["ing"]
        p copy            #=> ["ing"]

