I came up with some code in a dream that solved a problem once. I saw a little mental movie of an array being iterated through two by two, not one by one, and it looked like this

foo,bar,baz,quux
 |___| 

foo,bar,baz,quux
         |___|
[download]

and it turned out to be not a bad solution to the problem.
--

($_='jjjuuusssttt annootthheer
     pppeeerrrlll haaaccckkeer')=~y/a-z//s;print;
[download]