I' dunno well your skills but if you have not understood what the venerable monk tobyink says below, and directly answering to your cited above assertion:

the <> diamond operators consumes @ARGV so if you save a safe copy in @preserved you can refill @ARGV when you need ie first line of the two subs in the tobyink's example above.

As said below the <> diamond can also feed @ARGV opening SDTIN as last resource, so the above works because it restores @ARGV original contents at the top of the two testing subs.

L*