The logic expression will likely not do what you want. But as you haven't told us what you actually want to do, it's kinda hard to guess. What do you consider "correct"?

Most likely, you want:

if (   $fields[6] eq '"KOTB"' 
    or $fields[6] eq '"KBBA"'
    ...
    or $fields[6] eq '"KBBT"') {
  print "Inside the Check"
}
[download]

... but again, you should tell us more about what you have, what happens, what you expect to happen, and what you've tried so far.