use strict;
my $prev;
my $dup=0;
my ($ifile, $ufile, $dupfile) = qw(data uniq dups);

open(IN, $ifile) or die "Cannot open $ifile: $!\n";
open(UNQ,">", $ufile) or die "Cannot open $ufile: $!\n";
open(DUP, ">", $dupfile) or die "Cannot open $dupfile: $!\n";

while (<IN>) {
  if (defined($prev)) {
    if ($prev eq $_) {
      $dup = 1;
      print DUP $prev;
    } else {
      if ($dup) {
	print DUP $prev;
	$dup = 0;
      } else {
	print UNQ $prev;
      }
    }
  }
  $prev = $_;
}
  if (defined($prev)) {
      if ($dup) {
	print DUP $prev;
	$dup = 0;
      } else {
	print UNQ $prev;
      }
  }