To think that one’s contrition is literally perfect is to think that we have merited sanctifying grace by our own works, which is a sin of presumption. We can never know whether our contrition was perfect.
Now, we must understand what is meant by
perfect in the context of the Catechism:
My opinion: to avoid confusion, let perfect = first type (unofficial wording, of course). A contrition “of the first type” is one that arises from a love by which God is loved above all else (“ex, from the act of contrition prayer:
most of all because they offend You, my God, who are all-good and deserving of all my love”).
Now my point is: this contrition “of first type” is the type of contrition that, united to the
firm resolution to confess as soon as possible, obtains forgiveness of mortal sins. However, how can we be sure that we made a
perfect contrition “of first type”? I already know that something within me is moved to repentance partially for fear of being eternally separated from God (contrition of fear, or, for the sake of the argument, “of second type”

).
That’s the issue as far as I can see it: I try that my contrition be always of the perfect type (of charity) and never of the imperfect type (of fear), but I can never be sure that it was perfectly of charity, that is (for the grand finale, replacing my unofficial “of first type” with the official word), I can never be sure that my contrition was
perfectly perfect
I hope the above makes sense!