Simply saying Perl is slow sounds to me like "I didn't really try that hard".

Sometimes it is, sometimes it isn't. I know (from profiling :-) that heavily numeric stuff like GAs and neural nets that Perl is just too darn slow. The interpreter overhead on tight loops and the overhead of dealing with scalars instead of raw integers just gets in the way.

Sometimes there's a nice Perl module sitting there I can use that drops down to something faster, but if there isn't I have to amble off into XS or Inline:: land.

Since I don't like C if I can avoid it I'm likely to go for Lisp, which I can usually tweak enough to be substantially faster than the equivalent Perl.

With any luck better compilation techniques in Parrot/Perl 6 will mean that I can stay in Perl more often on those few occasions when I need to write something that ends up CPU bound.