I should have taken the time to respond properly but I had a meeting to go to and just /msg'd you. My point was that there is nothing preventing two different installations/versions/configurations of Perl from having one or more of the same @INC paths. This may or may not be a good thing. Compatability usually comes into question at some point. You can modify @INC in several ways -
Chances are you wouldn't unintentionally cross paths and if you did do so intentionally it is because you know what you are doing. For those who get strange error messages with multiple versions - this might be something to look at. I have personally had problems with a Cygwin installation and ActiveState.