chansen made a standalone pure perl FCGI daemon using his Net::FastCGI - so I converted it into Plack handler :) http://bit.ly/dwEFAU
Christian Hansen demonstrated his pure perl FastCGI handler based on his Net::FastCGI module on IRC #plack by pasting the code. 15 minutes later, I whipped up Plack::Handler::FCGI::PP, which now passes Plack::Test::Suite PSGI compatibility test using tokuhirom's FCGI::Client as a testing tool.
Including this FCGI handler in Plack core is a big win since FCGI.xs is known to be a really legacy bad XS code. The pure perl FCGI handler is on topic/fcgi-pp branch now and will be merged when we're more confident and probably add more compelling features such as preforking manager support.