You can search for the string "(KB\d+)" at the end of line.

while (<DATA>) {
  if (m/\((KB\d+)\)\s*$/) {
    print "$1\n";
  }
}
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Update: Sorry, I made a mistake here (0600 here, what do you think :)). You can use this approach:

# Change default separator to \n"
$/ = "\n\"";
while (<DATA>) {
  # Put " in the beginning of line.
  $_ = qq/"$_/ unless m/^"/;
  # Removes \n
  s/\n/ /g;
}
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