It might be easier to write out a regular expression for this:

while (<INFILE>) {
    chomp;
    m/(\d+)\s+\(\((\d+)\s+(\d+)\s+(\d+)\)\s*\((\d+)\s+(\d+)\s+(\d+)\)\
+)/;
    $L = $3 + $6;
    $D = $2 + $5;
    $M = $4 + $7;
}
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Well, it seemed like a good idea... (and it does pass the given test case)