sub fib (Int $n) { return 1 if $n < 2; state @seen[$n] //= fib($n-1) + fib($n-2); } #### sub fib (Int $n) { $n < 2 or state @seen[$n] //= fib($n-1) + fib($n-2); } #### my&fib:={$_<2or state@s[$_]//=fib($_-1)+fib $_-2}