Use the resource machinery to fetch/cache/unpack/... the App::cpanminus
tarball.
- this hardcodes the version, I can't figure out how to use a variant to
hold/set the value and access it in the resource().
- change up the install to use the `with working_dir()` meme.
Make running perl's tests conditional, one must now specify the
`--run-tests` flag to the `spack install` command in order to run the
tests.
On one system (8 core, 16GB Digital Ocean Droplet), installing without
tests takes 3 minutes, with tests takes 16 minutes.
Rather than hard-coding the verison of `cpanm` that's [optionally]
installed into the core, make it a variant with a default value of
'1.7042'.
Also discovered that `prefix + 'bin'` is the same as `prefix.bin`, so
embetter that bit of code.
Add perl package, based on [work by
justintoo](https://github.com/LLNL/spack/pull/105). He had too many
things pulled into that pull request, this just adds a perl package.
Support the current releases on the past three minor branches.
Run perl's tests before installing.
Install cpanm into the core (makes building on top of this perl *much*
simpler). Controlled by a variant.
