my @samples =
(
   [  [ 1, 2, 3, 4 ], [ 5, 6, 7, 8 ] ],
   [  [ 1, 3, 5, 7 ], [ 2, 4, 6, 8 ] ]
);

my $sample;
foreach $sample (@samples)
{
   my @set = @$sample; 
   my @in  = @{$set[0]};
   my @out = @{$set[1]};
   
   print "in: @in  out: @out\n";
}