When the first version of Rakudo Star came out, I was eager to try it, but I was, erm, somewhat underwhelmed by the fact that its performance was not quite up to what some people might have expected:

$ time ./perl6 -e 'my $s; for 1..10000 {$s+=1/$_**2};say $s'
1.64483407184806

real 0m38.387s
user 0m38.154s
sys 0m0.232s

$ time perl -E 'my $s; for (1..10000) {$s+=1/$_**2};say $s'
1.64483407184806

real 0m0.009s
user 0m0.008s
sys 0m0.004s
[download]

One year later, I've tried the same "benchmark" with Rakudo Star 2011.07:

time ./perl6 -e 'my $s; for 1..10000 {$s+=1/$_**2};say $s'
1.64483407184806

real    0m9.588s
user    0m9.513s
sys    0m0.068s
[download]

Well, it's an improvement.

Now, the latest version (2012.01) came out, supposedly with great improvements, so I thought I'd try it.

To my great consternation the same script didn't complete within three minutes. I tried to lower the loop range:

time ./perl6 -e 'my $s; for 1..1000 {$s+=1/$_**2};say $s'
NaN

real    0m2.164s
user    0m2.080s
sys    0m0.080s
[download]

Note that the result is incorrect (it is a number actually).

I've tried other ranges:

A very pronounced O(N²) trend can be observed here. Is this a known problem? Because it is a problem: there is nothing in the algorithm that would imply such a quadratic behavior, and indeed, with Rakudo 2011.07, elapsed time grows linearly with the number of iterations.

As to the NaN,

./perl6 -e 'my $s; for 1..358 {$s+=1/$_**2};say $s'
1.64214466837792

./perl6 -e 'my $s; for 1..359 {$s+=1/$_**2};say $s'
NaN
[download]

To paraphrase a certain presentation about weird programming languages that's become popular lately,

WAT