15 days in Malaysia: what to see after Borneo and before the Perhentians?

Hi! I’m planning a 15-day trip to Malaysia. The idea is to visit KL for 2 or 3 days, then Borneo, and I’m wondering what to do with the rest of the time. I’d like to finish with the Perhentian Islands... What do you think? Any tips or advice would be great—I’d really appreciate it!