Inability to install multiple versions of the same package can be a feature. It encourages the creation of stable, backwards-compatible packages.
That's what I wish the language designers had avoided. It would be convenient for users if there were never any reasons to want anything but the most recent version.
I know Perl and similar languages tend to value rapid development over complete reliability, but I'd prefer not to think about version numbers or worry about updates that break things. Maybe if the package management systems had been designed with less rope, users would more rarely get hung.