I can't be sure of your data since you didn't provide it. Is the code to handle it most like #1, #2, or #3 below?

my @arr1;
while ( <> ) {
    my @arr = split ',', $_;
    ( push @arr1, $arr[0] ) if  $arr[2] eq 'particular';
}
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my @arr1 = grep { @{$_}[2] =~ /particular/ } @arr;
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my @arr1 = grep { %{$_}{'FILETYPE'} eq 'particular' } @arr;
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If you can't answer that, then you'll need to provide your input and desired output.

Problems have solutions. If you can't define a desired state and explain how it is different from the current state then you don't have a problem. You have a gripe. Gripes don't have solutions other than turning them into problems. Note that this doesn't mean that the solutions to all problems are feasible, but stating the problem is a much better start than griping.