while (<>) {
	print unless seen_bucket($_);
}
__END__

Ten sets of 1..400 should get uniq'd to 1..400

$ perl -le 'for(1..10){for(1..400){print}}' | perl dup.pl | wc -l
    400

Ten sets of 1..401 should get uniq'd to (1..401) x 10 because
2 buckets of 200 lines hold upto 400 

$ perl -le 'for(1..10){for(1..401){print}}' | perl dup.pl | wc -l
   4010