plackup /home/moo/post-echo.psgi -r
Watching /home/moo/lib /home/moo/post-echo.psgi for file updates.
HTTP::Server::PSGI: Accepting connections at http://0:5000/

##</code><code>##

moo@cow[2258]~>curl http://0:5000/
OHAI GET

moo@cow[2259]~>curl http://0:5000/ -X HEAD
OHAI HEAD

moo@cow[2260]~>curl http://0:5000/ -X POST
POST http://example.org/
User-Agent: ...snip...

moo@cow[2261]~>curl http://0:5000/ -d "internet=cats in tubes"
POST http://example.org/
Content-Length: 22
Content-Type: application/x-www-form-urlencoded

internet=cats in tubes

##</code><code>##

curl http://0:5000/ -F code=@/home/moo/post-echo.psgi
POST http://example.org/
Expect: 100-continue
Content-Length: 2408
Content-Type: multipart/form-data; boundary=----------------------------2db0025e93ba

------------------------------2db0025e93ba
Content-Disposition: form-data; name="code"; filename="post-echo.psgi"
Content-Type: application/octet-stream

#!/usr/bin/env perl
# filename: post-echo.psgi
use strictures;
use Plack::Request;
use HTTP::Request;

sub {
    my $env = shift;
    my $request = Plack::Request->new($env);

    my $response = $request->new_response(200);
    $response->content_type("text/plain; charset=UTF-8");
    if ( $request->method eq "POST" )
    {
        $request->input->read( my $buffer, $request->header("Content-Length"), 0 );
        my $rerequest = HTTP::Request
            ->new( "POST", "http://example.org/" , $request->headers, $buffer );

        $response->body( $rerequest->as_string );
    }
    else
    {
        $response->body("OHAI " . $request->method . "\n");
    }
    $response->finalize;
};