use strict;
use GDBM_File ;

my %hash;

tie %hash, 'GDBM_File', 'words.dbm', &GDBM_WRCREAT, 0640;

my $dict_file = '/usr/share/dict/longlist';

open DICT, "<$dict_file" or die "open($dict_file): $!";

my @words = ();
my $prefix = '';

while(<DICT>) {
  chomp;
  $_ = lc($_);
  if(substr($_, 0, 3) ne $prefix) {
    if(@words) {
      $hash{$prefix} = join(' ', @words);
      @words = ();
    }
    $prefix = substr($_, 0, 3);
  }
  push @words, $_;
}

untie %hash ;