plack/Plack — pull request #339 by doy (2012-10-15 21:31:32+00:00)
Title: fix errordocument for streaming responses in subrequests

Assigning directly to $res->[2] is wrong here, because the app itself could be using streaming, in which case it expects to receive a writer object back, but servers determine whether to return a writer object based on if the third element exists.