Although you may miss the warnings (without FATAL), there's a 100% chance your customers will see them.

What kind of broad assumption are you making here? Lots of people work in environments where their customers come via a webserver. A webserver which logs the messages found on STDERR instead of sending them over the line to the customer.

My customers prefer a page that just does the right thing, instead of dying when Perl behaves like a toddler spotting a spider because it saw a comma inside a qw.

Warnings are warnings. Cases where Perl thinks, you're probably just right, and I will carry on, because, really, there's nothing actually holding me back, but just in case, you may want to look at this one of these days. Warnings most definitely are not errors. On errors, Perl dies. On warnings, it continues. Rightly so.

Now, for me, if there's anything I'd change about use warnings;, it's changing the use to a no. Or perhaps:

no warnings 'all';
use warnings 'uninitialized';
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