my $ERRORCOUNT=0;
my %HASH;
my %OTHERHASH;
...
foreach my $LINE (@LINES)
{
   # the sub-routine works and is returning the desired output
   my ($vlan, $mac, $int, $counter) = linesifter($LINE);

   if ($error eq 1)
   {
      ERRORCOUNT++;
   } 
   else
   {
      my @VLANS, @MACS, @INTS);
      push $HASH{$MACS[$mac]}, [$VLANS[$vlan], [$INTS[$int]];
}

# here will follow similar code from another file 

# compare $HASH[$MACS[keymatch]] to $OTHERHASH[$MACS[$keymatch]] 
# then do *magic* and line up all items that are referenced by matching MAC key in both files onto one line. Store in a file. 

sub linesifter
{
#...
#...omitted
  # various regex'es for grep'ing data
#...
return ($vlan, $mac, $int, $error);
}

##</code><code>##

#!/usr/bin/perl 
#
#
use strict;
use warnings;

use File::Glob ':globally';

my @SHOW_ARP = <~/Documents/show_outputs/*arp*.txt>;
my @SHOW_MAC = <~/Documents/show_outputs/*mac*.txt>;
#my $CLEAN_ARP_REC = '~/Documents/clean_arp.tmp';
#my $CLEAN_MAC_REC = '~/Documents/clean_mac.tmp';

my $CLEAN_ARP_REC = '/home/gtreptow/Documents/show_outputs/clean_arp.tmp';
open (OUTPUT, "> $CLEAN_ARP_REC") or die "Could not open $CLEAN_ARP_REC."; 

# my global hash that should contain all my matches

#my %ARP_HASH = ();	
my %MAC_HASH;
my (@VLANS, @MACS, @INTS);

foreach my $FILES (@SHOW_MAC)
{
	open (INFILE, '<', $FILES);
	print "using file: $FILES\n";
	my $FAILCOUNTER = 0;
	my $COUNTER = 0;

	chomp (my @LINES = <INFILE>);
	
	foreach my $LINE (@LINES)
	{
		my ($VLAN, $MAC, $INT, $COUNTER) = &mac_linesifter($LINE);		# Call sub-routine "linesifter" and pass every line to it
		if ($COUNTER eq 1) 
		{
			$FAILCOUNTER++;
			#print "Saw an INCOMPLETE\n";				# Test each line
		}
		else		
		{	
			#print "$VLAN \t $MAC \t $INT \t $COUNTER \n";
			
			#$MAC_HASH = {};
			#$MAC_HASH->{MAC}= "$MAC";
			#$MAC_HASH->{VLAN}="$VLAN";
			#$MAC_HASH->{INT}="$INT"; 
			my ($VLANS, @MACS, @INTS);
			push @{ $MAC_HASH{$MACS[$MAC]} }, [$VLANS[$VLAN] ,$INTS[$INT]];
		}
	}

# we also need to get the hostname

print "!!! $FAILCOUNTER ARP records ignored due to incomplete entries !!!\n";
print "\n";
print "Contents of Hash ARP_HASH:\n";
foreach my $VALUE (sort keys %MAC_HASH)
{
	print "$VALUE, $ARP_HASH{$VALUE}[0],$ARP_HASH{$VALUE}[1],$ARP_HASH{$VALUE}[2]\n";
}

}
close (OUTPUT);

### BEGIN SUB-ROUTINE 2 ###

sub mac_linesifter
{
	my ($LINE) = @_;
	my $VLAN;
	my $MAC;
	my $INT;
	my $COUNTER = 0;
	
	if ($LINE !~ m/^\*/)  							# skip if line does not start with "*"
	{	
		$COUNTER=1;
		no warnings "exiting";
		next;
	}
	if ($LINE =~ m/^\s*$/)							# skip empty lines
	{
		$COUNTER=1;
		no warnings "exiting";
		next;
	}
	if ($LINE =~ m/static/)						# skip static entries
	{
		$COUNTER=1;
		no warnings "exiting";
		next;
	}
	if ($LINE =~ m/(^\*\ [0-9]*)/)						# match VLAN identifier 
	{
		# remove leading "* "
		$VLAN = substr($1,2);
	}
	if ($LINE =~ m/([0-9a-f]{4}\.[0-9a-f]{4}\.[0-9a-f]{4})/)			# match MAC
	{
		$MAC = $1;
	}
	# match either - example Eth101/0/48", Eth12/1, Po12 - add regex here for additional interace type matches
	if ($LINE =~ m/([A-Z]{1}[a-z]{2}[0-9]*\/[0-9]*\/[0-9]*|[A-Z]{1}[a-z]{2}[0-9]*|[Po]{2}[0-9]{2})/)
	{
		$INT = $1;
		#print "int match: $1\n";
	}
	return ($VLAN, $MAC, $INT, $COUNTER);					# return these values from sub-routine
}

### END SUB-ROUTINE 2 ###