And with only a few tweaks, we can decrement strings:

#!/usr/bin/perl

use strict;
use warnings;

my $consonants = 'BCDFGHJKLMNPQRSTVWXZ';

my @letters = split //, $consonants;
my ($first, $last) = @letters[0, -1];
my %prev;
@prev{@letters} = ('', @letters);

my $x = 'BCD';
while( length $x )
  {
  print "$x ";
  $x =~ s/(.)($first*)$/ $prev{$1} . $last x length $2 /e;
  }
print "\n";
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