This is one I have never understood the right answer, because in the Canon it says the absolution is as we understand it to be “I absolve you from your sins…”, but it does not say anything for guidance like “any small variation is invalid” like it does in other areas.
Then I found the answer! —>
If you go to the Radio section of CA, and listen to the second hour of Sept. 21, you will hear Bishop Salvatore Cordileone, who is a Canon Lawyer also, do a show “Ask a Canon Lawyer”. Someone asked this exact same question and 25% of the way into the show, and here is what he said (paraphrased):
He said that if the words of absolution the priest uses are a slight discrepancy and most importantly convey the same meaning, the absolution is valid. The reason for this was very interesting - he said that in the sacrament of confession, the words of absolution are Church-given, as opposed to Christ-given; so they are still to be followed, but slight variations with the same meaning do not affect validity.
This is contrasted to sacraments like Baptism or the Consecration of the Eucharist, where the words given to us are from Christ, so the must be followed exactly and to the letter otherwise it is an invalid baptism/consecration.
If you listen to the Bishop, he seems to really know his stuff, and given he is not only an informed Canon lawyer and a Bishop, I will believe that this is truth. AndI learned something in the process!