Another brute force method that puts all words in 2of12inf.txt in 8 letter classes and counts their members. Runs 40mins on my machine.

use strict;
use warnings;
use Data::Dumper;

sub fits {
  my( $class, $subclass ) = @_;
  return 0 if length( $class ) < length( $subclass );
  $class =~ s/$_// or return 0 for split //, $subclass;
  return 1;
}

open my $dict, "<", "2of12inf.txt" or die "Cannot open dictionary!\n";
my $words = do { local $/; <$dict> };
close $dict;

my @words = sort { length($b) <=> length($a) } sort $words =~ /\b(\w{1
+,8})\b/g;

my %classes;
my $cnt = 0;
for my $w (@words) {
  my $ws = join '', sort split //, $w;
  my $fitted = 0;
  for my $class (keys %classes) {
    if( fits( $class, $ws ) ) {
      $classes{$class}{$w}++;
      $fitted++;
    }
  }
  $classes{$ws}{$w}++ unless $fitted;
}

my @sorted = sort { scalar keys %{$classes{$b}} <=> scalar keys %{$cla
+sses{$a}} } keys %classes;
for( @sorted ) {
  print "$_: ", scalar keys %{$classes{$_}}, "\n";
}
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and here are my top ten:

aeinprst: 346
aeilprst: 344
adeiprst: 332
aeimprst: 328
adeilrst: 319
adeoprst: 316
aeilnpst: 314
adeinrst: 313
aeloprst: 313
aeilnrst: 312
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