c) a custom/standalone perl install in your $HOME

Yep - that's me.
About 40 different perl version-configuration variants that have accumulated over the last few years - all sitting in their own separate directories.
Just run ls ~, copy the one I want to the clipboard, run export PATH=~/<paste>/bin:$PATH ... and then run perl -v if I want to check that I've got the one I intended.
Probably not the cleverest approach, but it suits me fine.

Mostly I'm just running the current stable perl version of the day - of which there's at least 3 different configurations to choose from, in recent years.
The older versions are just there for reference, and because there's no reason to remove them.

Cheers,
Rob