All statements end in a semicolon. Statements also can include other statements, in the body of a MOO command. The for loop is a statement, and the 'body' of the for loop contains a statement. This is also a nested statement, one statement in a the body of the fork, and the fork counts as a statement. Statements are made up of commands or expressions.
Commands tell the moo to do something.
Commands do not return values. Commands can take expressions as arguments, but commands can't be used as arguments. Expressions return a value. It returns 0. In this case, the expression is 1, which returns 1.