Here's an example where I try to install Tree::DAG_Node.

root@dizzy# perl Makefile.PL
Writing Makefile for Tree::DAG_Node
root@dizzy# make
make: *** No rule to make target `/usr/lib/perl/5.8Config.pm',
  needed by `Makefile'.  Stop.
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You'll notice there's a slash missing in the filename. I've found that that's because in `Makefile' there is no line such as:

DIRFILESEP = /
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Normally that's in the "MakeMaker constants section". So I tried adding that to the Makefile.

root@dizzy# make
make: *** No rule to make target `blibdirs', needed by `config'.  Stop
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I notice on a working system that there's a "MakeMaker blibdirs section" in the Makefile. On my broken system there is no such section.

The last lead I have is that ExtUtils::MakeMaker, unlike all other modules I've tried, does install fine! But it always installs even though it's already up to date.

UPDATE (2005-11-10): I forgot to mention that I've tried reinstalling every Perl package I could think of. Although it's testing/unstable, I have another such system that is fine. The broken machine tends to go long periods without updates, so maybe a package(s) didn't upgrade quite right. Or maybe someone here has hacked away at it.. I wish I at least knew what the problem files were. It's probably something silly and trivial.