{ use vars qw( @cache @n ) } {@cache = (0, 1)} sub fib { {push @n, shift} {return pop @n if $n[-1] < 2} {$cache [$n[-1]] ||= fib ($n[-1] - 1) + fib ($n[-1] - 2)} {return $cache[pop @n]} } #### { use vars qw( @cache ) } {@cache = (0, 1)} sub fib { (local (our $n = shift)) && do { {return $n if $n < 2} {$cache[$n] ||= fib ($n - 1) + fib ($n - 2)} {return $cache[$n]} } } #### { use vars qw( @cache ) } sub fib { (local (our $n) = shift), ( $n < 2 ? $n : $cache[$n] ||= fib ($n - 1) + fib ($n - 2) ) }