Apart from a few built-in keyword operators such as and, or, not, operators always consist of these characters: + - ∗ \ / < > = @ $ ~ & % ! ? ^ . | User define

Apart from a few built-in keyword operators such as and, or, not, operators always consist of these characters: + - ∗ \ / < > = @ $ ~ & % ! ? ^ . | User defined operators are allowed. Nothing stops you from defining your own @!?+~ operator, but readability can suffer. The longest one I saw in the tutorial was a -+- operator in the set operations. (Note: one of the legal operators in an asterisk, which I transcoded to a similar looking unicode character to avoid offending the HN quote system. It really is an asterisk, not whatever your browser displayed.)