My just-released CodeGen::Cpppp requires 5.20 because I required lexical subs, and wanted template authors to be able to use sub signatures and 5.20 is the earliest version that supports it. I enable the 'use experimental' for them behind the scenes. I think this is a fairly reasonable target version because it's been out for a long while and there's simply no good way to back-port subroutine signatures if you're advertising them to users of the module.

Meanwhile, most of my modules will continue to be ~5.8 because 5.8 can do most of anything that needs done, sometimes with some shims to work around bugs. I don't *need* to use subroutine signatures for my own benefit, and indeed they sometimes slow down the code a bit so all the more reason to leave them out of modules if the purpose of the module is performance.

I don't see any reason to support before 5.8 because I've not heard of a single person still using one of them. Also before 5.8 doesn't have weakrefs, and I consider those to be mandatory for any language that is based on reference counting.

Edit

Actually, I'm debating moving all my modules to 5.10 so that I can use //. While I can write that as defined $x? $x : ... the // is cleaner and also more performant.