#!/usr/bin/perl

use strict;

my @AoH = (
       {a => 1,  b  => 2,  c  => 3},
       {a => 1,  b  => 2},
       {a => 1,  b  => 2,  c  => 3,  d  => 4},
       {a => 1}
);

my @AoH_sorted = sort { keys(%{$AoH[$b]}) <=> keys(%{$AoH[$a]}) } @AoH;

foreach my $i (0 .. $#AoH_sorted) {
  print "$i\t";
  if (exists  $AoH_sorted[$i]) {
    my %hash = %{$AoH_sorted[$i]};
    foreach my $key (keys %hash) {
      print "$key\t";
    }
  }
  print "\n";
}