The diamond operator reads from ARGV, not STDIN.
That's not quite true

choroba is correct though, in that <> is always equivalent to <ARGV>, as is described in the very documentation you referenced. The magical behavior you describe is not that of the <> operator in general, it is that of the ARGV filehandle, which modifies @ARGV in order for STDIN to be read automatically via the ARGV handle.

Reworded for clarity, shortly after posting.

In reply to Re^3: Override "null filehandle" by haukex
in thread Override "null filehandle" by BillKSmith

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