The code uses regular expressions to match and search for the pattern "back" in different strings. The first if statement uses the match method to check if the pattern matches "backup.txt", which it does, so sum is incremented by 1. The second if statement uses the match method to check if the pattern matches "text.back", which it does not, so sum remains the same. The third if statement uses the search method to check if the pattern is found in "backup.txt", which it does, so sum is incremented by 4. The fourth if statement uses the search method to check if the pattern is found in "text.back", which it does, so sum is incremented by 8. Therefore, the final value of sum is 13.