foreach my $s1 (@set1) {
     foreach my $s2 (@set2) {
          foreach my $s3 (@sizes) {
               foreach my $s4 (@colors) {
                    print "$s1$s2$s3$s4\n";
               }
         }
     }
} 

##</code><code>##

my @sku   =  qw/SKU1 SKU2 SKU3/;
my @tslh  =  qw/t s l h/;
my @colors = qw/BLU GRN WHT BLK /;  
my @sizes = qw / S M L XL 2X /;

print map { $col = $_; map { $siz = $_; map {$a1 =$_; map "$_ $a1 $siz $col\n", @sku;} @tslh} @sizes } @colors;

##</code><code>##

SKU1 t S BLU
SKU2 t S BLU
SKU3 t S BLU
SKU1 s S BLU
SKU2 s S BLU
...
SKU3 l 2X BLK
SKU1 h 2X BLK
SKU2 h 2X BLK
SKU3 h 2X BLK