The subref is of course overhead, but you might want to keep it as named sub for multiple use.

Or just eliminate it entirely using a do-block instead of indirecting it with a subroutine:

my $dir = shift;
my @list = grep /\.java$/ , do {
    if (opendir my $dh, $dir) {
      my @l = readdir $dh;
      closedir $dh;
      @l;
    } else { () }
  };
[download]

-- Randal L. Schwartz, Perl hacker