my %hash = (
	'key1' => [1, 20, 3],
	'key2' => [1, 30, 4, 7],
	'key3' => [1, 9, 8],
	'key4' => [1, 9, 17],
	'key5' => [1, 9, 17],
);

my %rev_hash;

while(my ($k, $v) = each %hash) {
	push @{$rev_hash{$_}}, $k for @$v;
}

##</code><code>##

$_ = join ' ', sort @$_  for values %rev_hash;

my %inv_hash;
while(my ($k, $v) = each %rev_hash) {
    push @{$inv_hash{$v}}, $k;
}

##</code><code>##

$_ = join ' ', sort {$a<=>$b} @$_  for values %inv_hash;

my %revinv_hash = reverse %inv_hash;