Coworker #2 notes that I can have the best of both worlds, developing in warnings and sending out to production without warnings (see ENVIRONMENT or PERL5OPT in perlrun).

Oh, c'mon! This comes out quite so often... it seems like (some) people thinks that code in production is not code that should be further maintained any more, possibly by other people. How is code commited out into production? Do they expect one to comment the use warnings; line just before claiming his code to be production ready and to uncomment it on next development cycle? And what if the next developer to take over the code does not know about this "tradition"? (Let's hope he'll be of the school of thought it must be uncommented forever...) Much better to leave it as it is and just like quite everybody here has been suggestiong, (make it warnings free and) adopt a logging system for the wanted warnings. That's how I've seen things done at my last job, and more serious warnings and errors triggered more "invasive" means to draw attention, from emails to groups of people to sms'es to their personal phones.