Here's an example where a naive Perl 6 version is going to beat the pants off of the naive version in another language:
Find the sum of all integers from 10 to 1000000 inclusive.
In Perl 6:
say [+] 10 .. 1000000
This finishes almost immediately. (It also does so if the endpoint is 10¹⁰⁰⁰ or more)
The reason is if you use the built in version of the &infix:«+» operator, it calls the sum method on the Range object. That particular method knows how to calculate the sum on the Range without iterating through the values. If you modify the &infix:«+» operator lexically it won't take that shortcut.
This also works the same if you wrote it like this:
say Range.new(10,1000000).reduce(&[+])
There are plenty of areas where Rakudo Perl 6 is slower than I would like, but for many uses it is fast enough.
It's remarkably slow right now.. It takes 1.5 minutes to generate an image. I tried to do the same thing in Julia and it takes 1.5 seconds. So I guess I must be doing something wrong!