$ time perl -e '
print fibo(99);
{
  my @cache;
  sub fibo {
    my $num = shift;
    unless (defined $cache[$num]) {
      if ($num < 3) {
         $cache[$num] = 1; 
      } else { 
         $cache[$num] = fibo($num-1) + fibo($num-2);
      }
    }
    return $cache[$num];
  }
}
'
2.18922995834555e+20
real    0m0.036s
user    0m0.000s
sys     0m0.031s