`get_computer_choice`

   195     sub get_computer_choice {
   196        my @available_choices = @_;
   197        my $length = @available_choices;
   198        my $number = int(rand() * ($length - 1));
   199        my $choice = $available_choices[$number];
   200        return $choice;  ## this will be a coordinate, in the form of $x$y from $z above
   201     }

This is wasteful

           sub get_computer_choice {
              my $length = @_;
              my $number = int(rand() * ($length - 1));
              my $choice = $_[$number];
              return $choice;  ## this will be a coordinate, in the form of $x$y from $z above
           }

           sub get_computer_choice {
              my $number = int(rand() * (@_ - 1));
              return $_[$number];
           }