#! perl -slw
use strict;
use Data::Dump qw[ pp ];
use List::Util qw[ reduce ];

our $N //= 1;


my %byFreq = map{
    int( rand 1000 ) => $_
} 'A'x$N .. 'Z'x$N;
pp \%byFreq;

my @tree;
reduce{
    $a->[0] = $byFreq{ $b };
    $a->[1] = [];
} \@tree, sort{ $a <=> $b } keys %byFreq;

pp \@tree;