op.c: Warn on "return $a or $b" [perl #59802]

op.c: Warn on "return $a or $b" [perl #59802]

Add a warning for the (likely) unintended use of "return $a or $b"
(and similar expressions), which perl parses as "(return $a) || $b"
(which is effectively just "return $a;").

Note this warning is triggered by some modules (e.g. Test::Builder).
These are not fixed by this commit.

Signed-off-by: Niels Thykier <niels@thykier.net>