for my $word ( split /\s+/, $text ) {

    for my $pre ( keys %hash ) {

        for my $post ( keys %hash ) {
            #- Kleinschreibung
            my $lc_word="\L$word";
            my $lc_komposit="\L$pre$post";

            if ( $lc_word eq $lc_komposit ) {
                print $word, $/;
            }
        }
    }
}