print "\nEnter your words (separated by spaces): >> ";
chomp(my $line = <STDIN>);
my @words = split /\s+/, $line;

for($i = 0; $i <= ($#words-1); $i++) 
{
	for($j = $i+1; $j <= $#words; $j++)
	{
		print  "========================================\n";
	print  "\t", ucfirst(@words[$i]),"\t", ucfirst(@words[$j]),"\n";
		print  "========================================\n";
		local $/=undef;
		print grep{!/(@words[$i,$j])/}<DATA> =~ m!(<MS_\d+>.*?</MS_\d+>)!gs if /(@words[$i,$j])/;
	}
}
__DATA__
<MS_1>
  <loc>c:\data\cat.xml</loc>
  <words>dog, cat, fish, bird</words>
</MS_1>

<MS_2>
  <loc>c:\data\cow.xml</loc>
  <words>dog, cat, fish, bird, cow, goat</words>
</MS_2>

<MS_3>
  <loc>c:\data\snake.xml</loc>
   <words>dog, cat, fish, bird, snake, orange</words>
</MS_3>