my $sets = [
	[1,2,3,3,3,3,4,5,6,7,8,9,10],
	[1,1,1,2,6,7],
	[3,4,5,5,5,5,6,6,6,6,7,8,9],
];

my %hash = map { $_, 1 } @{$sets->[0]};
for(my $i=1; $i<scalar(@{$sets});$i++) {
	%hash = map { $_, 1 } grep {%hash->{$_}} @{$sets->[$i]};
}

return (keys(%hash));