sub getmatrix {
  my $what = shift;
  my @matrix;
  while (<STDIN>) {
    chop;
    if (/^0-9 ]/) die "Not a legal matrix row!\n"; }
    push @matrix, split / /;
  }
  return @matrix;
}

##</code><code>##

sub checkmatrix {
  my $rowlength = @$_[0];
  for (@_) {
    $rowlength == @$_ or die "Number of columns was not consistant!\n";
  }
}

##</code><code>##

sub getdimen {
  my $rows = @_;      # get number of rows
  my $cols = @$_[0];  # get number of elems in first row
  return ($rows,$columns);
}

##</code><code>##

sub getproduct {
  my ($aref, $bref) = @_;
  my @a = @$aref; my @b = @$bref;
  my @product;
  checkmatrix(@a);
  checkmatrix(@b);
  my ($arow, $acol) = getdimen(@a);
  my ($brow, $bcol) = getdimen(@b);
  $acol == $brow or die "The matrices can't be multiplied!\n";

  for $i (0..$arow) {
    for $j (0..$bcol) {
      for $k (0..$acol) {
        $product[$i][$j] += $a[$i][$k] * $b[$k][$j];
      }
    }
  }
  return @product;
}