open(IN,  $ifile);
open(UNQ, $ufile);
open(DUP, $dupfile);

my %seen;

while (<IN>) {

    if ( exists( $seen{$_} )) {
        print DUP "$_\n";
    }
    else {
        $seen{$_}++;
        print UNQ "$_\n";
    }
}
close(IN);
close(UNQ);
close(DUP);