#!/usr/bin/perl -w
use strict;
use 5.010;  #for new //= operator

use Data::Dump qw(pp);

my @all_arrays = ([1 .. 20],
                  [10 .. 30],
                  [19 .. 40],
                 );

my @unique_descriptive;

foreach my $num (map{@$_}@all_arrays)
{
   $unique_descriptive[$num]++;  #simple peg counter
}

# add a column to the 2-D array with row number
# undef counts as freq of zero, the //=0 does that

my $i=0;
@unique_descriptive = map{[$i++,$_//=0]}@unique_descriptive;

@unique_descriptive = sort{ $a->[1] <=> $b->[1]  #by freq
                                    or
                            $a->[0] <=> $b->[0]  #by peg number
                          }@unique_descriptive;

foreach my $row (@unique_descriptive)
{
   print "num = $row->[0] \tfreq=$row->[1]\n" if ($row->[1] > 0);
}