How about something like:

  open (IN, $file) or die "$!\n";
  my @ary = <IN>;
  close IN;
  open (OUT, ">$file") or die "$!\n";
  print OUT "stuff\n";
  print OUT @ary;
  close OUT;
[download]

or

  rename $file, $tempfile;
  open (OUT, ">$file") or die "$!\n";
  print OUT "stuff\n";
  open (IN, $tempfile) or die "$!\n";
  while (<IN>) {
     print OUT $_; 
  }
  close IN;
  close OUT;
[download]

Update: or better yet, see broquaint's post above.