1)how to open a file like >+ or +<?.

From perldoc -f open:

You can put a '+' in front of the '>' or '<' to indicate that
you want both read and write access to the file; thus '+<' is
almost always preferred for read/write updates--the '+>' mode
would clobber the file first. You can't usually use either
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Curiously enough I wrote an explicit example yesterday in a thread with almost exactly the same subject as this one...