my @array1 = ('lots', 'of', 'nice', 'words');
my @array2 = ('red','clothes', 'are', 'fun');
my @array3;
if (scalar @array1 == scalar @array2) {
  $array3[$_] = $array1[$_] . $array2[-($_ + 1)] for (0 .. $#array1);
}

print "@array3\n";