It just doesn't look right. You are trying to use junctions, which are not available in Perl 5.

If you have perl 5.10.0, you can use smart match instead:

if ($fields[6] ~~ qw("KOTB" "KBBA" "KBBC" "KBBM" "KBBT")){ 
   ...
}
[download]

Or you can use a regex match (with any perl version):

if ($fields[6] =~ m/\A"(?:KOTB|KBB[ACMT])"\z/){
    ....
}
[download]