sub checkForLetters {
    my ($sentence, $wantedLetters)=@_;

    # don't need this variable (or any of them, in
    # fact -- they're just here for clarity.
    # we could work straight out of @_ if we wanted
    # this terser
    # Also, the $[ check is just pedantic - if someone
    # changes $[, shoot them.
    my $foundLetters=scalar (grep index($sentence,$_)>=$[,
                                  split //,$wantedLetters);

    return length($wantedLetters)==$foundLetters;
}