If it's asking for the source directory, it intends to have you rebuild apache and/or the shared object library mod_perl.so. If this is not they way you plan to go, you can install from binaries. Many linux distros use a package manager called RPM. In this case you would download the .rpm version and run the fllowing command from the shell:
rpm -ivh packagename.rpm
If you are running on Windows, you would download the .exe or .msi versions. If none of these work for you, let us know what you have and we will walk you through the steps.