my @sorted =  sort @AoA; #sort on $a
my %seen = ();
my $j = 0;
while ($j < $#sorted) {
    my $var = shift;
    my $b = $var[1];
    my $c = $var[2];
    if ( ! $seen{$b}++ ) { # $b not seen before
        DO STH WITH $b AND $c
        $seen{$b}++;
    } else { #seen $b before
        my ($b, $a) = RESAMPLE;
        # sort remaining array, from now on... and proceed analyzing line by line
    }
}