I did a little checking, and the verse actually says, "Be ye therefore perfect, even as your Father which is in heaven is perfect. (Mat 5:48).
The phrase "even as" carries the idea of "just like" or "exactly like". We know that this is not possible in this life, but the Bible also says that when He appears (the Second Coming), we shall be like Him. That could include perfection, once we have been changed into glorious bodies like unto His own. At that point, we will be free from sin.
There is also this interesting verse in Hebrews: "To the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect," (Heb 12:23)
Do you think that the "perfection" the bible speaks of is of the same degree as that of the Father? I don't.
I don't think anyone will ever be as perfect as God is perfect.
If all things are to be brought under Him who is above all, then there is at least that area in which they have not attained unto the perfection of God.
Feel free to answer this off-line. I'm not interested in a debate.