From this thread Scalars, Lists, and Arrays guess that is called a list expression and not a list itself. :)

I think pg's example could have been something like this -  my @a = (1,2,3); my @b = (@a,4,5,6); here we use an array a in creating another array b. I think this just demonstrates that one can use arrays to create other arrays (you don't always need scalars separated by commas)...However I would not use the phrase arrays can contain arrays because once the array a is flattened under the list context the final array b just contains scalars

In short I agree with halley.