use strict;
use warnings;

my $second_file = "npn.txt";
open my $fh2, '<', $second_file or die "Cannot open  $second_file $!";
my %contents = map {chomp; $_ => 1} <$fh2>;
close $fh2;

my $first_file = "first_file.txt";
open my $fh1, '<', $first_file or die "Cannot open  $first_file $!";
while( my $line = <$fh1>) {
    chomp($line);
    my $field2 = (split /,/, $line)[1];
    print $line and next unless defined $field2;
    print $line unless defined $contents{$field2};
}
close $fh1;
[download]

Looks like a ferfect task for Text::CSV_XS's csv using a filter:

$ cat npn.txt
11111111
10001781
11111222
[download]

$ cat first_file.txt
abc,,,,
abc,10001781,,,
abc,10001782,,,
abd,10001783,,,
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$ cat test.pl
use strict;
use warnings;
use Text::CSV_XS "csv";

my %npn = map { chomp; $_ => 1 } do { local @ARGV = "npn.txt"; <> };

csv (in => "first_file.txt", filter => { 2 => sub { !exists $npn{$_} }
+});
[download]

$ perl test.pl
abc,,,,
abc,10001782,,,
abd,10001783,,,
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I am new to perl scripting. I have 2 new input files, file1 and file2. I have to retrieve second field of each record from first file and check if it is existing in second file, file2. I have read file2 contents and stored it in an array. Please find my file2(npn.txt) contents below:

11111111
10001781
11111222
[download]

abc,,,, 
abc,10001781,,,
abc,10001782,,, 
abd,10001783,,,
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Based on above files, what my record should contain:

abc,,,, 
abc,10001782,,, 
abd,10001783,,,
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abc,10001781,,, 
abc,10001782,,, 
abd,10001783,,,
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Can anyone please guide me what is the bug in this. Please find my code snippet below:

...
open (info, "<npn.txt");
chomp (@contents = (<info>));
close info;


$record = $_."~";
@flds = split(/\,/, $record);

if (grep !/^$flds[1]/, @contents) {
 
  print $record;
}
' >hi5res.txt
[download]

Your grep returns all the elements of @contents that are NOT matched by your regex, so that will always be true. Removing the ! from your grep should fix that, assuming the rest of the code that we can't see is okay.

This is not the best way to do this, though, because you're looping through the contents of one file for each line in the other file. The standard way to "match lines from one file to keys from another file" is to load the keys from one file (file2) into a hash as its keys, then go through the other file (file1) splitting out the matching part and seeing if it exists as a key in the hash. If it does exist, print it.

Try coding it that way, and let us know if you need help.

Aaron B.
Available for small or large Perl jobs and *nix system administration; see my home node.

It should be working for you

use strict;
use warnings;

my $second_file = "npn.txt";
open my $fh2, '<', $second_file or die "Can't write to '$second_file':
+ $!\n";

my @contents;
chomp (@contents = (<$fh2>));
close $fh2;

my $first_file= "hi5res.txt";

open my $fh1, '<', $first_file or die "Can't write to '$first_file': $
+!\n";

while( my $eachLine=<$fh1>)
{
        chomp($eachLine);
        my @array = split(/,/,$eachLine);

        print $eachLine if (not defined $array[1]);

        if (grep {$_ eq $array[1]} @contents) {
                  print "$eachLine\n" ;
          }

}
[download]

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All is well. I learn by answering your questions...