# pseudocode
sub find_some ( @choices, @alphabet ) {
    $results = [];
    for $choice ( @choices ) {
        if ( choice_is_in_alphabet ) {
            @new_choices  = @choices  - $choice;
            @new_alphabet = @alphabet - letters_in( $choice );
            push @$results, [ $choice, find_some( @new_choices, @new_alphabet ) ];
        }
    }
    return $results;
}