Perl Monks, I need some assistance better understanding an issue. I have a script that compares two files and produces an output of differences from the second file . The issue I am having is adding an additional code to produce the differences from the first file it does not output anything or produce any errors. Below is my script. 

#!/usr/local/bin/perl

use strict;
use warnings;

my $a_file;
my $b_file;

# quit unless we have the correct number of command-line args
my $num_args = $#ARGV + 1;
if ($num_args != 5) {
    print "\nUsage: name.pl new_filename orig_filename domain new_tool
+s orig_tools\n";
    exit;
}

#  args
my $new_filename=$ARGV[0];
my $orig_filename=$ARGV[1];
my $domain=$ARGV[2];
my $new_tools=$ARGV[3];
my $orig_tools=$ARGV[4];
my $psconfig = "psconfig.sh";

if ($new_filename eq $psconfig) {

$a_file = "/directory/$new_filename" ;
$b_file = "/directory/$orig_filename" ;
}

open my $a_fh, '<', $a_file  or die "file error $a_file: $!";
open my $b_fh, '<', $b_file  or die "file error $b_file: $!";

my %second_file;
print "\n--------------------------------------------\n";
print "Output from $new_tools $domain $new_filename\n";
print "--------------------------------------------\n";

@second_file{map { unpack 'A*', $_ } <$b_fh>} = ();

while (<$a_fh>) {
    print unless exists $second_file{unpack 'A*', $_};
}

my %first_file;
print "\n--------------------------------------------\n";
print "Output from $orig_tools $domain $orig_filename\n";
print "--------------------------------------------\n";

@first_file{map { unpack 'A*', $_ } <$a_fh>} = ();

while (<$b_fh>) {
    print unless exists $first_file{unpack 'A*', $_};
}

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In reply to output using map by coding_new

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