How do I create a hash of hashes in Perl?

Question

Based on my current understanding of hashes in Perl, I would expect this code to print \"hello world.\" It instead prints nothing.

%a=();

%b=();
$b{str} = \         


        

Answer 1

Perl likes to flatten your data structures. That's often a good thing...for example, (@options, "another option", "yet another") ends up as one list.

If you really mean to have one structure inside another, the inner structure needs to be a reference. Like so:

%a{1} = { %b };  

The braces denote a hash, which you're filling with values from %b, and getting back as a reference rather than a straight hash.

You could also say

$a{1} = \%b;   

but that makes changes to %b change $a{1} as well.