Bitwise OR on the two arguments. The arguments are converted to a number. A List, Dict or Float argument causes an error. Also see and() and xor(). Example: :let bits = or(bits, 0x80) Can also be used as a |method|: :let bits = bits->or(0x80) Rationale: The reason this is a function and not using the "|" character like many languages, is that Vi has always used "|" to separate commands. In many places it would not be clear if "|" is an operator or a command separator.