E.g., does perl avoid copying of data in the following cases?

No. The array is copied in both those cases.

There are two ways of avoiding that:

1. Return an arrayref as in your second example and use it as an array ref in the calling code:

   sub large_array_ref {
     my $large_array_ref = [];
     ...populate @$large_array_ref...
     return $large_array_ref;
   }
   
   my $c = large_array_ref();
   
   $c->[ ... ];
   [download]

2. Pass an array ref into your sub:

   sub large_array_ref {
     my $large_array_ref = shift;
     ...populate @$large_array_ref...
     return;
   }
   
   large_array_ref( \my @c );
   
   $c[ ... ];
   [download]

   With a suitably chosen name for the sub, the latter looks less awkward:

   populateThingArray( \my @c );
   
   $c[ ... ];
   [download]