#! perl -w
use strict;
use Data::Dumper;

# if the number of fields was to vary you could generate the combinations using an algorithm.
my @sets = (
	[1,2,3], 	# 1st (index 0) field can be combined with these other fields.
	[0,2,3],	# 2nd with these...
	[0,1,3],
	[0,1,2]
);

my %hash;

my @labels = split/\s+/, <DATA>;    # read the labels from the first line of the DATA...

while (<DATA>) {
	chomp;
	my @fields = split;
	
	for my $index (0 .. $#sets) {
		
		$hash{ $labels[$index] }{ $fields[$_] } =
			$fields[$index] 
				for (@{$sets[$index]}[0 .. 2]);
	}
}
print Dumper(\%hash);

__DATA__
mac				ip		name		file
ABCDEFABCDEF10	10.0.0.1	www.foo1.com	afilename1
ABCDEFABCDEF02	10.0.0.2	www.foo2.com	afilename2
ABCDEFABCDEF03	10.0.0.3	www.foo3.com	afilename3
ABCDEFABCDEF04	10.0.0.4	www.foo4.com	afilename4
ABCDEFABCDEF05	10.0.0.5	www.foo5.com	afilename5
##</code><code>##

$VAR1 = {
          'ip' => {
                    'www.foo5.com' => '10.0.0.5',
                    'ABCDEFABCDEF02' => '10.0.0.2',
                    'ABCDEFABCDEF10' => '10.0.0.1',
                    'ABCDEFABCDEF03' => '10.0.0.3',
                    'www.foo2.com' => '10.0.0.2',
                    'ABCDEFABCDEF04' => '10.0.0.4',
                    'ABCDEFABCDEF05' => '10.0.0.5',
                    'afilename1' => '10.0.0.1',
                    'afilename2' => '10.0.0.2',
                    'afilename3' => '10.0.0.3',
                    'www.foo3.com' => '10.0.0.3',
                    'afilename4' => '10.0.0.4',
                    'afilename5' => '10.0.0.5',
                    'www.foo4.com' => '10.0.0.4',
                    'www.foo1.com' => '10.0.0.1'
                  },
          'file' => {
                      'www.foo5.com' => 'afilename5',
                      'ABCDEFABCDEF02' => 'afilename2',
                      'ABCDEFABCDEF10' => 'afilename1',
                      '10.0.0.5' => 'afilename5',
                      'ABCDEFABCDEF03' => 'afilename3',
                      'www.foo2.com' => 'afilename2',
                      'ABCDEFABCDEF04' => 'afilename4',
                      'ABCDEFABCDEF05' => 'afilename5',
                      'www.foo3.com' => 'afilename3',
                      'www.foo4.com' => 'afilename4',
                      '10.0.0.1' => 'afilename1',
                      'www.foo1.com' => 'afilename1',
                      '10.0.0.2' => 'afilename2',
                      '10.0.0.3' => 'afilename3',
                      '10.0.0.4' => 'afilename4'
                    },
          'mac' => {
                     'www.foo5.com' => 'ABCDEFABCDEF05',
                     '10.0.0.5' => 'ABCDEFABCDEF05',
                     'www.foo2.com' => 'ABCDEFABCDEF02',
                     'afilename1' => 'ABCDEFABCDEF10',
                     'afilename2' => 'ABCDEFABCDEF02',
                     'afilename3' => 'ABCDEFABCDEF03',
                     'www.foo3.com' => 'ABCDEFABCDEF03',
                     'afilename4' => 'ABCDEFABCDEF04',
                     'afilename5' => 'ABCDEFABCDEF05',
                     'www.foo4.com' => 'ABCDEFABCDEF04',
                     '10.0.0.1' => 'ABCDEFABCDEF10',
                     'www.foo1.com' => 'ABCDEFABCDEF10',
                     '10.0.0.2' => 'ABCDEFABCDEF02',
                     '10.0.0.3' => 'ABCDEFABCDEF03',
                     '10.0.0.4' => 'ABCDEFABCDEF04'
                   },
          'name' => {
                      'ABCDEFABCDEF02' => 'www.foo2.com',
                      'ABCDEFABCDEF10' => 'www.foo1.com',
                      '10.0.0.5' => 'www.foo5.com',
                      'ABCDEFABCDEF03' => 'www.foo3.com',
                      'ABCDEFABCDEF04' => 'www.foo4.com',
                      'ABCDEFABCDEF05' => 'www.foo5.com',
                      'afilename1' => 'www.foo1.com',
                      'afilename2' => 'www.foo2.com',
                      'afilename3' => 'www.foo3.com',
                      'afilename4' => 'www.foo4.com',
                      'afilename5' => 'www.foo5.com',
                      '10.0.0.1' => 'www.foo1.com',
                      '10.0.0.2' => 'www.foo2.com',
                      '10.0.0.3' => 'www.foo3.com',
                      '10.0.0.4' => 'www.foo4.com'
                    }
        };