Installing Perl 5.10 Breaks Ubuntu

After installing Perl 5.10 from source, Ubuntu’s package manager had a fit. Looking at the terminal screen gave the following:

It seems like Debian put its Perl packages into a weird place. A Google search led me to this information at Perlmonks.

I tried the suggested solution there:

It seems to have fixed the problem with the package manager.

This leaves me with some queries:

1. How do I alter @INC to point to a directory like the above?
2. What motivated Debian to put the Perl modules in such a non-standard place? Why not just put them in the standard directories, where Perl can find them, and where cpan can add new packages as usual?
3. Am I stuck with a system which is going to break every time I try to install new software?

This kind of problem is pretty nasty and also a huge time sink.

I noticed on the net that some people write

at the top of their Perl 5.10 scripts. Perhaps it’s a better way for the time being.