@matrix =([1,5,7],
          [2,3,4],
          [5,1,9],
          [7,8],
          [3]);

for my $y(0..$#matrix) {
    my @row=@{$matrix[$y]};
    for my $x(0..$#row) {
        print "Value $row[$x] at x $x y $y\n";
    }
}