IMO nested data structures are always difficult, but Perl adds more difficulty early on. The only easy data structure you can pass around is the flat list, or some scalars in front of a flat list. Creating a complex data structure is "just some syntax", but accessing data in it requires learning about references and dereferencing.

Python for example makes accessing complex data structures easier, because it does not flatten argument lists. There is the nasty surprise later on, when you realize that you need the equivalent of Storable::dclone, because in Python just like in Perl, all complex elements of hashes and arrays are still references. But you don't need to know that just to pass parameters more complex than a list to a function, and retrieve them in that function.