Ugly, off-the-top-of-my-head idea. This depends on having no space characters in the keywords - I suppose you can use \0 as a separator if you need to, but I found ' ' easier to type: 
use Math::Combinatorics;

my $nwordsatonce = 4;
my ($k,$v);
my %totals = ();
local $" = ' ';  # just in case
while (($k,$v) = each %items)
{
  next unless $nwordsatonce <= @$v;
  my @words = sort @$v;
  do {$totals{"@$_"} += 1;} for combine($nwordsatonce,@words);
}

my @comb = sort {$totals{$b} <=> $totals{$a}} keys %totals;
print "Top $nwordsatonce - word combinations:\n";
do {print "$_\n";} for @comb[0..4];

[download]
I'm a bit curious where this data is coming from. 
--
@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/;
map{y/X_/\n /;print}map{pop@$_}@/for@/

[download]

In reply to Re: algorithm for 'best subsets' by fizbin
in thread algorithm for 'best subsets' by halley

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