my @var = 1 .. 38;
while ( @var ) {
   my @splice = splice @var, 0, 10;
   print "@splice\n";
}

sub BUILD_REQUESTS {
  foreach my $device (keys %hash) {
     my @vlans = keys %{$hash{$device}};
     while ( @vlans ) {
         my @splice = splice @vlans, 0, 10;
         # mache jetzt etwas mit den 10 vlans in @splice
     }
  }
}