Comments may not be nested. The programming language has a number of statement types. The simplest is an expression statement, an expression that is not part of any other statement or expression. An expression statement is evaluated, and if its value is non-zero, it is assumed to be a string, and written to the program output file. If its value is zero, nothing is written.
Square brackets indicate optional parts of the statement syntax.
An if statement is executed by first evaluating the conditional expression in the if clause. If non-zero, the statements in the if clause are evaluated, and the rest of the if statement, if any, is ignored. If the value is zero, and there is an elsif clause following, the conditional in the elsif clause is evaluated, and if non-zero, the statements in that clause are executed. Conditionals are evaluated until one of them is non-zero, or until there are no more. If no conditional is non-zero, and if the if statement ends with an else clause, the statements in the else clause are executed.