I would think most good programmers would not have a problem with running strict at all times, but in case they don't, the latter case can be easily resolved using:

ref( $fh ) && defined eval { fileno $fh }
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(At least, the quick spot checks that I've done indicate this works as expected for different indirect filehandle types).

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Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
"I can see my house from here!"
It's not what you know, but knowing how to find it if you don't know that's important