The song of Moses is part of Deuteronomy and in it is expressed the action of the divine Providence in history and teach about God:

He is the rock, his works are perfect,
and all his ways are just. A faithful God,
who does no wrong upright and just is he. Deuteronomy 32,4

The work of God is the same Divine Providence, the Providence is a divine attribute, this divine quality is upright, orderly, uplifting, without falsehood. God manifests himself in the Providence
We attribute to God the perfections that we see in the creation teach to us Thomas Aquinas, father of the scholasticism. Therefor we say that the works of God are gifts, the gifts are perfections.
It is true that in the universe there are imperfections, but these are states of deprivation. For example we say bad a man private of virtue. All being as being is good and it tends to his own perfection or nature, clarify the Theologist.
Example: the nature of the worm is the butterfly, the nature of every human community is the polis or city, city understand the self-sufficient community.
The man as God's work, insert in the history of the providence, is in a sense a perfection and its own nature is to achieve the conformity to his creator, for this the doctrine of the Kingdom of God.
That is the reason that man is co-creator with God by living the spiritual gifts received from him. Living the spiritual gifts is to search the correct and the best (remember that not all justice is correct, the justice is not a gift), the continuous improvement, the constant search for excellence.
Thus man perceives his destiny: to expand the gifts of God to the creation, improving the environment and the universe, think and act progressively, build, in short to increase the order of the universe.
It is so that ethically, that is to say on the plane of human choices and of Providence, that the expression in the Book of Deuteronomy isfulfilled: "the works of God are perfect"