use v5.12;
use warnings;
use Data::Dump qw/pp dd/;


my $X =
  [
   [1, -4, 7],
   [-2, 3, 3]
  ];

my $Y =
  [
   [8, -9, -6,  5],
   [1, -3, -4,  7],
   [2,  8, -8, -3],
   [1,  2, -5, -1]
  ];

pp $X;
pp $Y;

my $X_Y;
for my $x ( @$X ) {
    for my $y ( @$Y ) {
        push @$X_Y,
          [
           map {
               my $xx = $_;
               map { $xx * $_} @$y
           } @$x
          ];
    }
}

pp $X_Y;

##</code><code>##

[[1, -4, 7], [-2, 3, 3]]
[[8, -9, -6, 5], [1, -3, -4, 7], [2, 8, -8, -3], [1, 2, -5, -1]]
[
  [8, -9, -6, 5, -32, 36, 24, -20, 56, -63, -42, 35],
  [1, -3, -4, 7, -4, 12, 16, -28, 7, -21, -28, 49],
  [2, 8, -8, -3, -8, -32, 32, 12, 14, 56, -56, -21],
  [1, 2, -5, -1, -4, -8, 20, 4, 7, 14, -35, -7],
  [-16, 18, 12, -10, 24, -27, -18, 15, 24, -27, -18, 15],
  [-2, 6, 8, -14, 3, -9, -12, 21, 3, -9, -12, 21],
  [-4, -16, 16, 6, 6, 24, -24, -9, 6, 24, -24, -9],
  [-2, -4, 10, 2, 3, 6, -15, -3, 3, 6, -15, -3],
]