This eliminates the XS dependency in Plack.
Plack-1.0026-TRIAL is on CPAN, which is a big release that eliminated a dependency for the big LWP module.
LWP not only has a big chain of dependencies since the distribution split earlier, it also has XS dependency (HTML::Parser) in the chain, which makes Plack code non-trivial to install on environments without a C compiler, and makes fatpacking difficult (although realistically, these C bits are only necessary for testing and not required mostly on the runtime).
This is a big shift - I made LWP optional in #408 but also replaced the use of LWP with HTTP::Tiny in #410 - so that Plack::Test::Suite (reference Test suite for PSGI handlers) and ::Server (Plack::Test implementation to run tests through live server) now uses HTTP::Tiny instead of LWP. The test interface is still the same, and you can use HTTP::Request/Response interface for that, which is a much smaller subset of LWP.
I tested various distributions where it implicitly expects LWP when depending on Plack, and fixed a lot of them, and sent pull requests where needed. Please test Plack-1.0026-TRIAL against your application/frameworks/server implementations.
cpanm --dev Plack