while (my $line = <$fh>) {
    my $val = substr($line, $char_at, $num_chars);
    if ($val eq 'H' or $val eq 'T') {
        my $output = $line;
    }else {    
        chomp $line;
        next unless $line && length($line) >= $char_at;
        push @trnAccounts, substr($line, $char_at, $num_chars);
    }
}