use Data::Dumper;

my @a=(1..100);
my @a3=reform_list(3,@a);
print Dumper(@a3);
my @a4=reform_list(4,@a);
print Dumper(@a4);

sub reform_list{
  my $size=shift;
  my @list=@_;
  my @nlist=();
  my $max=int(scalar(@list)/$size);
  for(my $c=0;$c<=$max;$c++){
    my $a=$c*$size;
    my $b=($c+1)*$size-1;
    if($b>=scalar(@list)){
      $b=scalar(@list)-1;
    }
    if($a<=$b){
      push @nlist,[@list[$a..$b]];
    }
  }
  return @nlist;
}