Another approach is to go through it and "update" the code to work better with "current" perl and industry standards around usability and security.
If your boss is still programming, even he probably looks at his 'old' code and cringes a little bit. I had a very similar experience recently. While the company couldn't afford a complete re-write of that piece of code (not mission critical) he DID see the value in going through and making it run under strict and -w.
If the code IS mission critical, selling a re-write of the code to OO shouldn't be a problem. If there is any chance that this code will be used going forward, or if it has functions that might be used by other callers, this would be a good time to make those functions cleanly available to other callers.