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;