G'day Michael,

Thanks for the response. It's good to hear that you didn't encounter any problems with El Capitan.

"... unless you are doing some really OS specific things ..."

I don't really use the system's supplied applications except where I have to. I use Firefox instead of Safari; VLC instead of iTunes; Foxit instead of Preview; and so on. And, of course, as already stated, perlbrew Perl instead of system Perl.

"I have been holding off on Sierra, ..."

Assuming I do upgrade, which seems likely, it will happen in the next day or two. I'll report back with any issues and, if there were any, how I got around them.