my %hash=('ID' => { 'key1' => [key1_val1, key1_val2], 'key2' => [key2_val1, key2_val2] } ); #### 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; } } }