##
ID, 1, key1_val1, key2_val1
ID, 2, key1_val1, key2_val2
ID, 3, key1_val2, key2_val1
ID, 4, key1_val2, key2_val2
##
##
my $id2=1;
my %data=();
foreach my $id (keys(%hash)) {
foreach my $key1_val (@{$hash{$id}{'key1'}}) {
foreach my $key2_val (@{$hash{$id}{'key2'}}) {
$id2++;
$data{$id}{$id2}{'key1'}=$key1_val;
$data{$id}{$id2}{'key2'}=$key2_val;
}
}
}