ikegami has explained it very well and I feel that you are still missing something in your code that's why you are having a problem, try the below code, hope it helps you.
my %box = (
Milk => {
A => 5,
B => 10,
C => 20,
},
Chocolate => {
AB => 10,
BC => 25,
CD => 40,
},
);
foreach my $box_key(keys %box) {
foreach my $inside_key (keys $box{$box_key}) {
print "${box_key}_$inside_key is for rupees $box{$box_key}{$inside_key}\n";
}
}
Output:
Chocolate_CD is for rupees 40
Chocolate_BC is for rupees 25
Chocolate_AB is for rupees 10
Milk_A is for rupees 5
Milk_C is for rupees 20
Milk_B is for rupees 10