use 5.010;
use strict;
use warnings;
									# filehandle section
open STDOUT, ">ouiresults.txt";  	# Output file after program is run.
open STDERR, ">errlog.txt";      	# Error Log.
my $f1 = 'oui.txt'; 			 	# Filehandle of the OUI list from the IETF used to create a hash of oui and company.
my @data = ();					 	# Declared Array to be created with the input file for searching the MAC address.
my %hash = ();					 	# Declared Hash to be created with the input file to store the IP to MAC mappings.
my %oui = (); 						# Delcared Hash containing the OUI to Company mapping.

open (LIST1, $f1) || die "File not found\n";  		# Takes the oui file and creates a hash 
while (<LIST1>) {									# Key is OUI 
  chomp;											# Value is Company
  if (/[\x20]{5}\(base 16\)[\t]{2}/) {
     $oui{$`} = $';
  }
}
close LIST1;

open(INPUT, $ARGV[0]) || die "Cannot do eet! $!";  	# Takes the input file name on the command line and builds an array.
while (<INPUT>) {									# This is the ARP Cache file created from a copy/paste of a routers 
  push @data, "$_";									# show arp command.
}
close(INPUT);
													
for (@data) {     # This section iterates over the ARP cache array and pulls the IP and MAC address out and stores it into a hash
  if ($_ =~ m/([\d]+\.[\d]+\.[\d]+\.[\d]+).*([\w]{4})\.([\w]{4})\.([\w]{4})/i) {			# Key is MAC 
    my $temp = $2.$3.$4;																	# Value is IP
    $hash{$temp} = $1;
  }
}

while ( my ( $key, $value ) = each %hash  ) {
  my $match = substr $key, 0, 6;
  say "$hash{$key} mapped to $key for company $oui{$match}!";
}