$matrix =[
            [1,5,7],
            [2,3,4],
            [5,1,9],
            [7,8],
            [3]
          ];

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