FWIW you can localize a FH inside the function's scope, but this implies some glob syntax IIRC.

I think local *FH but ...

• I'd need to look it up
• it'll localize all other vars with the same symbol, like $FH too
• it's a dynamic runtime scope not a lexical, ie don't call another sub from inside which doesn't localize the same symbol before using it

Not that beginner friendly