fw() for 1 .. 10;
sub fw {
    my %uniq;
    for my $ix ( 0 .. 100 ){
        for my $key ( wf() ){
            my $count = $uniq{$key}++;
            if( $count > 1 ){
                my $keycount = keys %uniq;
                my $buckets  = %uniq;
                print "started repeating at iteration $ix after only $keycount in $buckets buckets \n";
                return;
            }
        }
    }
}
sub wf {
    my %f;
    $f{ [] } = [0];
    $f{ [] } = [1];
    $f{ [] } = [2];
    $f{ [] } = [3];
    return keys %f;
}
__END__
started repeating at iteration 8 after only 26 in 20/32 buckets
started repeating at iteration 4 after only 14 in 13/32 buckets
started repeating at iteration 5 after only 17 in 14/32 buckets
started repeating at iteration 5 after only 17 in 13/32 buckets
started repeating at iteration 5 after only 19 in 15/32 buckets
started repeating at iteration 5 after only 18 in 16/32 buckets
started repeating at iteration 6 after only 18 in 16/32 buckets
started repeating at iteration 7 after only 20 in 15/32 buckets
started repeating at iteration 6 after only 18 in 14/32 buckets
started repeating at iteration 7 after only 26 in 21/32 buckets