ananassa:

Your code is assuming that you're getting seven columns from your split on line 22. Then you're using several of those to do a regex match. However the last line of your file, for example, is likely empty (because many files end in a '\n'), causing you to have fewer than 2 columns fields array.

You might try something like:

...
my @fields = split /\t/, $item;
next if @fields < 7;
...
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...roboticus

When your only tool is a hammer, all problems look like your thumb.