use strict;
use warnings;

my $anchor = 1; # This is the basic element of the pairs we are looking for
my %results; # The final results will be found in this hash

foreach (<DATA>) {
	my %hash;
	foreach (split) {	# Put the array into a hash
		$hash{$_}=1;
	}
	if ($hash{$anchor}) { # Only process the hash if the anchor is present
		foreach (keys %hash) { # increment the frequencies in the results-hash
			++$results{$_} unless $_==$anchor; # but omit the anchor or the sort will not work!
		}
	}
}

for my $x(sort {return $results{$b} <=> $results{$a}} keys %results) {
    print "$x = $results{$x}\n";
}


__DATA__
2 4 5 7 8 10 
1 2 5 6 7 9 
2 6 7 8 9 10 
1 3 5 10 
1 3 4 5 6 8 9 
1 2 4 6 
1 2 4 5 7 10 
1 3 4 6 7 8 9