my @rows = qw/ 1 2 3 4 1 2 /; # 1 & 2 are dups
my @non_dupe_rows = do { my %seen;grep !$seen{$_}++, @rows };
print "@non_dupe_rows\n";

##</code><code>##

1 2 3 4

##</code><code>##

my @rows = qw/ 1 2 3 4 1 2 /; # 1 & 2 are dups
my @non_dupe_rows = do {
    my %seen; 
    $seen{$_}++ for @rows;
    grep $seen{$_} == 1, keys %seen
};
print "@non_dupe_rows\n";