This is now solved. It turns out LWP::Protocol::http replaces newlines in headers with spaces, and neither AnyEvent::HTTP, nor LWP::Protocol::AnyEvent::http did similar. Though the latter now does so with the latest CPAN update.

In reply to Re: Calling LWP/Mech from AnyEvent by Anonymous Monk
in thread Calling LWP/Mech from AnyEvent by Anonymous Monk

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