I might be wrong, but I am under the impression that you're not considering that queens can attack in columns as well as rows. You should also consider attacking squares that are "before" your current position, like in this untested snippet:

sub mark_attacks {
   my ($r,$c,$array) = @_;

   $array->[$r]->[$c] = 'Q';

   # mark everything

   my $none;

   for my $i (1 .. $SIZE) {
      $none = 1;
      $none = $array->[$r]->[$c + $i] = 0 if ($c + $i < $SIZE);
      $none = $array->[$r]->[$c - $i] = 0 if ($c - $i >= 0);
      $none = $array->[$r + $i]->[$c] = 0 if ($r + $i < $SIZE);
      $none = $array->[$r - $i]->[$c] = 0 if ($r - $i >= 0);
      $none = $array->[$r - $i]->[$c - $i] = 0 if ($r - $i >= 0 and $c
+ - $i >= 0);
      $none = $array->[$r + $i]->[$c + $i] = 0 if ($r + $i < $SIZE and
+ $c + $i < $SIZE);
      $none = $array->[$r - $i]->[$c + $i] = 0 if ($r - $i >= 0 and $c
+ + $i < $SIZE);
      $none = $array->[$r + $i]->[$c - $i] = 0 if ($r + $i < $SIZE and
+ $c - $i >= 0);
      last  if $none;
   }
}
[download]

I also think than a single loop might improve performance slightly.

Good luck in your assignment.

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.