I use 5.8 most of the time. Sometimes, I need to use 5.10.0, which I have in /opt/extras. To use 5.10.0, I normally do this:

/opt/extras/bin/perl5.10.0 script.pl

Or, for example, if I want to use CPAN to download pmtools:

/opt/extras/bin/cpan Devel::Loaded

Next, for example, I want to go back to 5.8 to check the path of Devel::Loaded:

pmpath Devel::Loaded

To check the path of Devel::Loaded in 5.10.0:

/opt/extras/bin/perl5.10.0 -S pmpath Devel::Loaded

Just a few ways of doing it. I hope it helps.