sub find_connection {
    # Find the indexes of the places where words can be
    # combined.
    # A hash array with array hashes will be returned;
    # The key of the hash is word1's index, word2 indexes for the
    # former are contained in the array.
    my ($word1, $word2) = @_;
    my $temp1 = $word1;
    my $index1 = 0;
    my %matches;
    while ($temp1 =~ /[\Q$word2\E]/) {
        my $letter = $&;                # The matched letter
        $index1 = $index1 + $-[0] + 1;  # The match index for w1
        $temp1 = substr($word1, $index1);

        my $temp2 = $word2;
        my $index2 = 0;
        while ($temp2 =~ /\Q$letter\E/) {
            $index2 = $index2 + $-[0] + 1;      # The match index for w2
            $temp2 = substr($word2, $index2);
            push(@{$matches{$index1}}, $index2); # Build a list of matches
        }
    }
    return \%matches;
}