Another place to look is in the INSTALL file which comes with the perl source. Of particular interest would be the "Coexistence with earlier versions of perl5" section, and possibly the earlier "installing perl under a different directory" area of the "make install" section.
in reply to Solaris, Perl 5.8 and use 5.005
I don't know if the above will help with your specific problem, but I found it quite useful in understanding what happens when I install a newer version on top of an older one. It also showed me why I had a different perl version in /usr/bin than I had in /usr/local/bin.