my $file = $indir . '/' . $lkp_file_name;

open(my $fh, '<', $file)
    or die "Cannot open file '$file' for reading: $!";

my @matched_lines = grep { /\Q$key_pattern/ } <$fh>;

close $fh
    or die "Cannot close file '$file': $!";

my @fields;

for my $line (@matched_lines)
{
    my    $field = (split /\|/, $line)[$data_location - 1];
    chomp $field;
    push  @fields, $field;
}

$final_data = join "\n", @fields;