hash => sub {
    while ( $data =~ /^(\d+) (\d+)/mg ) {
        next if exists $hash{$1} or exists $hash{$2};
    }
    return 1;
},
ahead => sub {
    while ( $data =~ /^(?!(?:0|15|16|31)\D)(\d+)\N{SPACE}
                       (?!(?:0|15|16|31)\D)(\d+)/mgx ) {
    }
    return 1;
},

        Rate  hash ahead
hash  1742/s    --  -31%
ahead 2541/s   46%    --