My solution was in Configure to say that the installed binaries should go into a tree below my home directory. Then I compiled and installed as me, thereby being utterly guaranteed of things like not messing up man pages. Perl didn't intend to install over them, and the OS wouldn't have let me even if Perl lied about what it was planning to do. (Perl didn't lie.:-)

Running multiple versions actually turned out to be ridiculously easy.