req.t

#!/usr/bin/env perl

use strict;
use warnings;

use HTTP::Message::PSGI qw(req_to_psgi);
use HTTP::Request;
use Plack::Request;
use Test::More;
use URI;

my $req = HTTP::Request->new(
    'GET',
    URI->new('http://example.com/'),
    [
        'Host' => 'another.example.com',
    ],
);

is $req->uri->host, 'example.com';

my $psgi_req = Plack::Request->new(req_to_psgi($req));

is $psgi_req->uri->host, 'example.com'; # !!!

done_testing;

req.t .............................. 
ok 1
not ok 2
#   Failed test at req.t line 24.
#          got: 'another.example.com'
#     expected: 'example.com'
1..2
# Looks like you failed 1 test of 2.
#FAIL ---
#

https://metacpan.org/source/HTTP::Message::PSGI#L29