Just for fun (and to stay sharp with Mojo), I went ahead and coded up a little example of calling another HTTP API and getting the response asynchronously:

#!/usr/bin/env perl
use Mojolicious::Lite -signatures;
use Mojo::IOLoop;
use Mojo::DOM;
use Mojo::UserAgent;
use Mojo::Util qw/dumper/;

my $OTHER_API = 'http://localhost:3000/second_api';

post '/toMFF' => sub ($c) {
    state $ua = Mojo::UserAgent->new;
    my $body = $c->req->body;
    my $dom = Mojo::DOM->new->xml(1)->parse($body); # example
    my $quz = $dom->at('bar[quz]')->{quz};
    $c->render_later;
    $ua->post_p( $OTHER_API => form => { quz => $quz } )
        ->then(sub ($tx) {
            my $res = $tx->result;
            my %stash = ( code=>$res->code, msg=>$res->message,
                timestamp => scalar gmtime, debugmessage=>"" );
            if ($res->is_success) {
                my $j = $res->json;
                $stash{debugmessage} = "Server response: ".dumper($j);
                if ( not $j->{response} ) {
                    $stash{code} = 599;
                    $stash{msg} = "Endpoint reported error";
                }
            }
            else { $stash{debugmessage} = "HTTP error" }
            $c->render('response', format=>'xml', %stash);
        })->catch(sub ($err) {
            # this sends a 500 response to the client:
            $c->reply->exception("The endpoint could not be reached: $
+err");
        });
};

# this API would actually be on a different server
post '/second_api' => sub ($c) {
    my $quz = $c->param('quz');
    my $resp = $quz && $quz=~/\S/
        ? { response => "Thanks for $quz!" }
        : { error => "You didn't provide a quz" };
    # pretend this API is a bit slow
    $c->render_later;
    Mojo::IOLoop->timer(1 => sub { $c->render(json=>$resp) });
};

app->start;

__DATA__
@@ response.xml.ep
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE cXML SYSTEM "http://xml.cXML.org/schemas/cXML/1.1.009/cXML.d
+td">
<cXML payloadID="foo@ceprinter.com" xml:lang="en-US" timestamp="<%= $t
+imestamp %>">
    <Response>
    <Status code="<%= $code %>" text="<%= $msg %>" />
    <!-- <%= $debugmessage %> -->
    </Response>
</cXML>
[download]

Test with e.g. curl -X POST http://127.0.0.1:3000/toMFF -H "Content-Type: application/xml" -d '<foo><bar quz="baz"/></foo>'