The documentation hints that the reason for not using setlogsock is that some people were using it without knowing what it did, and were making their code less reliable, rather than more so, by routinely writing setlogsock('unix').

Thanks for the pointers to other Syslog modules. I'd rather not resort to them because it would impose more work on the customers who have to run this program, but I'll go there (or just write the subset of syslogging that I actually need) if I can't make the program work acceptably in any other way.