Example, counter to https://gist.github.com/tempire/5621542, which shows how when the ua is prevent from going out of scope, the warning is not encountered and the process succeeds.

non_blocking_tx.pl

#!/usr/bin/env perl

use Mojolicious::Lite;

app->attr( ua => sub { Mojo::UserAgent->new } );

get '/' => sub {
  my $self = shift;
  $self->render_later;
 
  $self->app->ua->get( 'http://tempi.re' => sub {
    my ($ua, $tx) = @_;
      
    warn $tx->error; # premature connection close
      
    $self->render(text => $tx->res->body);
  } );

};

app->start;