Applying the KISS principle:

my @dirs; my @files;
for (readdir DIR) {
  next if $_ eq "." or $_ eq "..";
  if (-d "$base/$_") {
    push @dirs, $_;
  } else {
    push @files, $_;
  }
}
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Don't try to cooerce everything into a grep.

-- Randal L. Schwartz, Perl hacker