My Perl warnings are FATAL and I don't know why - apache

Question

I have two servers with the same configurations: httpd + mod_perl (I thought the settings were 100% the same), but in one server I got some perl warnings, while in the other server the same warnings get me FATAL errors. Look:
Server A log:
Use of uninitialized value in numeric eq (==) at
Server B log:
[Wed Jun 08 14:32:47 2016] [error] Use of uninitialized value in string eq at
In server A the request flow goes on and the user gets the desired result, but in server B the user gets a 500 error.
I am using
use strict;
use warnings;
in the file on both servers.
Any thoughts ?
Example of the code causing this warning/FATAL:
$allowed_sellers = any { $_ == $user->{user_id} } (111,123,222,345);
UPDATE:
I found this code in a module that I am using (Moo):
package Moo::_strictures;
use strict;
use warnings;
sub import {
if ($ENV{MOO_FATAL_WARNINGS}) {
require strictures;
strictures->VERSION(2);
#_ = ('strictures');
goto &strictures::import;
}
else {
strict->import;
warnings->import;
}
}
1;
But the env variable MOO_FATAL_WARNINGS seems to not be defined. Any thougts ?
SOLVED:
Guys, thanks a lot! We have finally discovered the problem: In server A the version of module Moo was 1.003 while server B was using a newer version 2.000001

Answer 1

Before version 2, calling use Moo; enabled strictures, which makes all warnings fatal except for a few categories. This caused a lot of problems*, so warnings are no longer fatal in version 2 and up.
To fix, upgrade Moo to the latest version. While you're at it, you should really fix the cause of the warnings, too.
* See the following discussions:
Default fatalization of warnings needs mst's clarification before new major strictures
fatal warnings are a ticking time bomb
Moo 2 and strictures 2