Looping through hash of arrays in Perl

Question

I have a hash of arrays, as follows: ``` my %hash = ( 234 => ["Larry", "Curly", "Moe"], 235 => ["bb", "ab", "aa", "ab", "bb"], 236 => ["aa", "ab", "bb", "aa", "bb"], ) ``` For each key in my hash, I would like to loop through each element of the array, assign that to a scalar variable so that I can process it, then move onto the next element of the array. Once I have processed all the elements of the array for a key, I want to onto the next key and individually process all of the elements of its array, and so on. I found and modified a snippet of code that iterates over the hash values (the array of each key in this case). Then I have a nested for-loop, that iterates over each element of that array. However, it's not doing what I expect it to. ``` for my $value (values %hash) { for (@$value) { my $index = shift($_); #process index } } ``` Error Message Not an ARRAY reference at [line number] For example, for the first iteration, I want `$index` to equal `Larry` so that I can process i…

Accepted Answer

The problem is that your list in `@$value` is already a list of your array elements, not arrays. Which is why you cannot use `shift` on it. All you need is:

```
for my $value (values %hash) {
    for my $index (@$value) {  # "Larry", "Curly", "Moe" etc
       ....
       #process index
    }
}
```

You probably don't want to use `shift` on your array anyway, since that will delete entries from your original structure.

Looping through hash of arrays in Perl

Solution

Problem