Here's a couple of interesting Perl alternatives:

  my @files = map { IO::File->new($_->[0], $_->[1]) || die $! } 
              ([shift, 'r'], [shift, 'w']);
  $files[1]->print( sort $files[0]->getlines );
  $_->close for @files;

And...

  use autodie;
  open my $out, '>', $ARGV[1];
  print {$out} sort do {open my $in, '<', $ARGV[0]; <$in>};