Control Data Corporation 3300 Reference Manual page 113

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IF statements within IF statements may be considered as paired IF and ELSE
combinations, proceeding from left to right. Any ELSE encountered is con-
sidered to apply to the immediately preceding IF that has not been already
paired with an ELSE.
When control is transferred to the next sentence, implicitly or explicitly,
control passes to the next sentence as written or to a return mechanism of a
PERFORM or a USE statement.
The following sentence contains two independent nests of conditional statements.
The first nest ends after the statement PERFORM procedure-name-2; the
second nest consists of the remainder of the sentence and has an implied
ELSE NEXT SENTENCE before the period. A, B, C, D, E, F each corresponds
to a conditional expression.
IF A; IF B PERFORM procedure-name-l ELSE NEXT SENTENCE
ELSE IF C NEXT SENTENCE ELSE PERFORM procedure-name-2
IF D PERFORM procedure-name-3 IF E PERFORM procedure-name-4
IF F PERFORM procedure-name-5 ELSE PERFORM procedure-name-6
ELSE STOP RUN.
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