use Perl

At the user's request, CPANdeps has sprouted another tentacle. There's now a ticky box which, if enabled, makes it also fetch MANIFEST files for the entire dependency tree, and highlight any modules (actually distributions) that don't look like they're pure perl. The heuristic is simple. We assume that a distribution is pure perl unless it contains a file that ends in .xs, .c or .h, or it depends on Inline::*. But if there is any file in the distro whose name contains the string 'pureperl' (case-insensitive, naturally), then we assume that the distribution contains a pure perl version as well as the C-ish version.

If there's any other things I should look for, please use the "report bugs" link on the website.