That certain operators (eof, open, etc.) have prototypes that aren't adequate for representing the syntax of the operator is the premise of the question.

For example,

• An overridden eof operator can't distinguish whether it was was called as eof or eof() while the real operator does.

• open( STDERR , ">&=", STDOUT ) is perfectly valid with the real operator, but throws a strict error with an overridden open.

  $ perl <<'.'
  use strict;
  open( STDERR , ">&=", STDOUT );
  BEGIN { *CORE::GLOBAL::open = sub (*;$@) { } }
  open( STDERR , ">&=", STDOUT );
  .
  Bareword "STDOUT" not allowed while "strict subs" in use at - line 4.
  Execution of - aborted due to compilation errors.
  [download]

Upd: Fixed accidental double negation.