#!/usr/bin/perl
use strict;
use warnings;
use Data::Dump;

srand 0;

my @aoa = (
    [map {int rand 3} 1 .. 10],
    [map {int rand 6} 1 .. 10],
    [map {int rand 20} 1 .. 10],
);

my @aof = map {{asFreq (@$_)}} @aoa;

print Data::Dump::dump (\@aof);


sub asFreq {
    my @elements = @_;
    my %freqs;
    
    ++$freqs{$_} for @elements;
    return %freqs;
}