moritz provided you with a programmatic solution to the question posed, having seen this test recently before I presume you want to ignore arrays that are sub arrays of other arrays in the array of arrays, yes?

If this is the spec you are trying to solve please provide us with either your work on it so far or at least how you would go about getting the result as a human being.

Describing the human steps taken to solve the issue and splitting them up into baby steps often provides useful pseudocode which can then be written in Perl.