The OPERATOR statement (OPR)
A typical OPERATOR statement may look like this:
OPERATOR (STRING) = (INTEGER) A1 &.OP.((REAL) V) (COMPLEX) A2
which creates an operator-function having the name OP, giving a string result from a left-hand side INTEGER operand A1, a right-hand side COMPLEX operand A2, and a REAL argument V.
The operands of an operator, as well as its arguments, can be assigned values in the text of the operator. This will only alter the operands in the caller if the operands are variables in the caller, rather than expressions or constants. This allows for assignment-type operators.