The files in /usr/lib/perl5/5.8.5/i386-linux-thread-multi/... wouldn't be compatible with 5.10.1. Binary modules for one major version of Perl (5.8) can't be used by a different major version of Perl (5.10).

If you want to test your modules with Perl 5.8.5, why don't you install Perl 5.8.5? You can have multiple version of Perl on the same machine. There's no need to remove Perl 5.10.1.