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+## "In [[..]], use || instead of -o.
+
+### Problematic code:
+
+    [[ "$1" = "-v" -o "$1" = "-help" ]]
+
+### Correct code:
+
+    [[ "$1" = "-v" || "$1" = "-help" ]]
+
+### Rationale:
+
+`-o` for logical OR is not supported in a `[[ .. ]]` expression. Use `||` instead.
+
+### Exceptions:
+
+None.
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