my %hash; @hash{0, 15, 16, 31} = ();

    # then add this to your benchmark
    hash => sub {
        while ( $data =~ /^(\d+) (\d+)/mg ) {
            next if exists $hash{$1} or exists $hash{$2};
            return 1;
        }
    },

##</code><code>##

             Rate  any_cr     any    ugly ugly_cr   hash2    hash
any_cr      865/s      --    -37%    -54%    -65%   -100%   -100%
any        1382/s     60%      --    -27%    -44%   -100%   -100%
ugly       1896/s    119%     37%      --    -24%   -100%   -100%
ugly_cr    2489/s    188%     80%     31%      --   -100%   -100%
hash    3084047/s 356493% 222992% 162532% 123813%     26%      --