When should I install my own language and library versions?

[Dan Ritter <dsr@randomstring.org>]

Generic answer, applying to all languages:

There are people who want a language (and libraries/modules)
installed because something else uses it. Those people should
definitely use the Debian-maintained versions.

Then there are people who want to develop software in a given
language. They can usually start off using the Debian-maintained
versions, but if they are serious about keeping up to date, they
will likely want to use an organized system to install multiple
versions of languages and libraries.

They need these for debugging older versions of their software,
testing out new versions, and ensuring consistency in their
builds.

Each language community tends to have its own tools for that.

-dsr-