Put shortly - you can't upgrade any of the crtical components - meaning Apache, PHP, Perl, MySQL - separately.
XAMMP (as been said in this forum hundreds of times) is a suite. All the parts are tailored to work together.
If you want speciifc version combinations, you should install the packages standalone and integrate them.
FYI - XAMPP is built with VC6 complied components. The components/extensions must also be for the same version of Apache, Perl, PHP etc. Mix and matcxh does not work.
Good luck with your project.