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 %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! $!";  	# Takes the input file name on the command line and builds a hash.
while (<INPUT>) {									# This is the ARP Cache file created from a copy/paste of a Cisco routers arp cache
  if ($_ =~ m/(\d+\.\d+\.\d+\.\d+).*(\w{4})\.(\w{4})\.(\w{4})/) {			# Key is MAC 
    my $temp = $2.$3.$4;																	# Value is IP
    $hash{$temp} = $1;
  }
}
close(INPUT);

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