$ perl -le'
my @A = ( [ 1, 2 ], [ 3, 4 ] );
print map "[ @$_ ]\n", @A;
my @B = ( [ 5, 6 ], [ 7, 8 ] );
print map "[ @$_ ]\n", @B;
my @A_B;
for my $x ( @A ) {
    for my $y ( @B ) {
        push @A_B, [ map( $x->[ 0 ] * $_, @$y ), map $x->[ 1 ] * $_, @$y ];
        }
    }
print map "[ @$_ ]\n", @A_B;
'
[ 1 2 ]
[ 3 4 ]

[ 5 6 ]
[ 7 8 ]

[ 5 6 10 12 ]
[ 7 8 14 16 ]
[ 15 18 20 24 ]
[ 21 24 28 32 ]