sub rekey {
	my $h = shift;
	for my $k (keys %$h) {
		next unless ref $$h{$k};
		my %n;
		for my $e (@{$$h{$k}}) {
			die "duplicate key '$$e{name}'"
				if exists $n{$$e{name}};
			$n{$$e{name}} = $e;
			rekey($e);
		}
		$$h{$k} = \%n;
	}
}
rekey( $foo );