Close. You need to count each array separately so that you can distinguish something appearing twice in one array from something that appears once in each array.

my @arr1 = qw(one one two three four four four);
my @arr2 = qw(two four four five five);

my %hash ;

++$hash{$_}[0] for @arr1;
++$hash{$_}[1] for @arr2;

for (keys %hash) {
  # Print the smaller count
  printf "$_ appears %d times in both arrays\n",
      $hash{$_}[0] < $hash{$_}[1] ? $hash{$_}[0] : $hash{$_}[1]
    if $hash{$_}[1] and $hash{$_}[0];
}
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