Yes these is a difference, as jeffa pointed out: precedence. As long as you use parentheses around e.d. open, it doesn't matter, but else it really makes a difference if you say:

open F, $file or die;
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which will die when the open failes, or:

open F, $file || die
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which will die if $file is false (undef, empty or 0), but NOT if the open fails!