use List::Util qw{ first };

sub subDiscarder {
    my @top3 = map [0, 0, -inf], 0 .. 2;
    for my $minion (@{ $_[0] }) {
        next if $minion->[2] < $top3[2][2];
        my $idx = first { $top3[$_][2] <= $minion->[2] } 0 .. 2;
        splice @top3, $idx, 0, $minion;
        splice @top3, 3;
    }
    @{ $_[0] } = @top3;
}