sub word_to_struct {
    my ( $word ) = @_;

    my %out;
    $out{$_}++ for split //, $word;

    return \%out;
}

sub read_dict {
    my ( $dict_file ) = @_;

    my %out;
    $dict_file ||= '/usr/share/dict/words';
    open my $dict_fh, '<', $dict_file
        or die "Can't read '$dict_file': $!\n";
    while ( my $word = <$dict_fh> ) {
        chomp $word;
        if ( $word =~ m{ \A [a-z]+ \z }xmsi ) {
            $out{$word} = word_to_struct($word);
        }
    }
    close $dict_fh or die "close failed: $!\n";

    return \%out;
}