Optimising Perl 6

sub fib-optimised-v5($n) { if $n > 1 { fib-optimised-v5($n - 1) + fib-optimised-v5($n - 2); } else { $n; } }

This is about 35-36% faster than the basic version.

It's still about 4.25 times slower than the basic Perl 5 version, but not too bad.