i work with clients that tend to take MONTHS for module installations, so i've been installing everything in my ~. just pass ./configure a --PREFIX=~/$wherever (even w/ -d), export PATH=~/wherever/bin:$PATH in your profile, and you're done. all modules get thrown in the ~/$wherever/lib hierarchy. i'm not sure if this is what you meant by 'co-exist', but it gives you independent perl installations; symlinks can always take care of any naming/path convention problems for ya. hth.