Nth fibonacci number with perl 6, adapted from http://blogs.perl.org/users/ovid/2015/02/avoid-a-common-software-bug-by-using-perl-6.html

nthfib.p6

use experimental :cached;

sub MAIN(Int $nth) {
  say fib($nth);
}

sub fib(Int $nth) is cached {
  given $nth {
    when 0  { 0 }
    when 1  { 1 }
    default { fib($nth-1) + fib($nth-2) }
  }
}

eric@eric-x240:hacks§ time perl6 nthfib.p6 1000
43466557686937456435688527675040625802564660517371780402481729089536555417949051890403879840079255169295922593080322634775209689623239873322471161642996440906533187938298969649928516003704476137795166849228875

real	0m0.627s
user	0m0.596s
sys	0m0.028s