That helps, thanks!

However, I still get an error "Use of uninitialized value in numeric comparison (<=>)" and it seems like the loop never ends...

@AoA[0..$#AoA] = sort { $b->[0] <=> $a->[0] } @AoA[0..$#AoA];
my %seen = ();
my $j = 0;
while ($j < $#AoA) {
    my $b = $AoA[$j][1];
    my $c = $AoA[$j][2];
    if ( ! $seen{$b}++ ) { # $b not seen before
        DO STH WITH $b AND $c
        $seen{$b}++;
    } else { #seen $b before
        my ($b, $a) = RESAMPLE;
        $AoA[$j][0] = $a;
        $AoA[$j][1] = '$b';
        @AoA[$j..$#AoA] = sort { $b->[0] <=> $a->[0] } @AoA[$j..$#AoA]
+;
    }
}
[download]

...any ideas?