@common = inter ( \%foo, \%bar, \%joe );
sub inter {
	my %seen;
	for my $href (@_) {
		while (my $k  = each %$href ) {
			$seen{$k}++;
		}
	}
	return grep { $seen{$_} == @_ } keys %seen;
}
=======================================================

##</code><code>##

__DATA__
my %foo = (
	'one' => 1,
	'two' => 2,
	'three' => 3,
);

my %bar = (
	'two' => 5,
	'four' => 6,
);

my %joe = (
	'three' => 7,
	'four' => 8,
	'five' => 89,
);

##</code><code>##

three five one two four