my %temp_for_compare;

# Add values from the first array into the temporary hash
$temp_for_compare{$_} = 0 for @array1;

# Now we can simply check the items in the second array against the hash
for my $val (@array2) {
   if (exists $temp_for_compare{$val}) {
      print "$val in both arrays\n";
   }
}

##</code><code>##

for my $a1val (@array1) {
   for my $a2val (@array2) {
      if ($a1val eq $a2val) {
         print "$a1val in both arrays\n";
      }
   }
}

##</code><code>##

my @tmpArray1 = sort @array1;
my @tmpArray2 = sort @array2;

# You run out of matches when either array is empty
while (@tmpArray1 and @tmpArray2) {
    if ($tmpArray1[0] eq $tmpArray2[0]) {
        print "$tmpArray1[0] in both arrays\n";
        shift @tmpArray1;
        shift @tmpArray2;
    }
    elsif ($tmpArray1[0] lt $tmpArray2[0]) {
        # tmpArray1 has an item not in tmpArray2, so get rid of
        # it and try the next element
        shift @tmpArray1;
    }
    else {
        # tmpArray2 has an item not in tmpArray1, so get rid of
        # it and try next element
        shift @tmpArray2;
    }
}