my @words = #...;

my %triples;
foreach (@words) {
  for (my $i = 0; $i < length($_) - 2; $i++) {
    push @{$triples{substr $_, $i, 3} ||= []}, $_;
  }
}

# Keep most popular triples
my @triples = grep { @{$triples{$_}} > 10 } keys %triples;

my %lensum;
foreach my $t (@triples) {
  foreach my $w (@{$triples{$t}}) {
    $lensum{$t} += length $w;
  }
}

@triples = sort { $lensum{$b} <=> $lensum{$a} } @triples;
my $re = join '|', map quotemeta, @triples;

while (<>) {
  print;
  my @hopes;

  while (/$re/gio) {
    push @hopes, @{$triples{$&}};
  }

  my $word = join '|', map quotemeta,
             sort { length($b) <=> length($a) } @hopes;

  1 while s/$word/[*]/i;
  print;
}