for $word (@large_wordlist) {
    $word = '_'.$word.'_';
    my $len  = length($word);
    my $flen = $len;    
    my $i;

    for ($i=0; $i<$flen; $i++) {
      $$ngram{substr($word,$i,5)}++ if $len > 4;
      $$ngram{substr($word,$i,4)}++ if $len > 3;
      $$ngram{substr($word,$i,3)}++ if $len > 2;
      $$ngram{substr($word,$i,2)}++ if $len > 1;
      $$ngram{substr($word,$i,1)}++;
      $len--;
    }
}