# your version
# my @tmp = readdir(DIR);
# my @files = map { "$dir/$_" } grep { !/^\.{1,2}$/ && -f "$dir/$_" } @tmp;
# my @dirs  = map { "$dir/$_" } grep { !/^\.{1,2}$/ && -d "$dir/$_" } @tmp;

# another version
my @files;
my @dirs;
my @tmp = grep { ! /^\./ } readdir DIR; # grep once.
foreach (@tmp) {
   if ( -d "$dir/$_" ) {                # stat once.
       push @dirs, "$dir/$_";
   } else { 
       push @files, "$dir/$_";
   }
}