I agree with the suggestion to visit Singapore. You could fly one way to save time and travel by bus in one direction and stop in Melacca enroute. With just five days, I'd spend more time in Singapore than KL. If Melacca and Singapore appeals to you, there are buses that travel from Melacca directly to KUL airport.

Another option is Siem Reap, Cambodia. Flights from KL aren't expensive, but MH flights aren't daily and you'd need to check if the flight schedule works with your travel dates. I would spend more time in SR than KL, hotels in SR are very cheap and hiring a private tuk tuk driver for a day isn't expensive either.