Control Data Corporation 3300 Reference Manual page 125

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Each procedure name is the name of a section or paragraph in the
Procedure Division.
Each identifier represents a numeric elementary item described in the Data
Division. In format 2, the identifier represents a numeric item with no
positions to the right of the assumed decimal point.
A literal must be numeric.
When the PERFORM statement is executed, control is transferred to the first
statement of procedure-name-I. An automatic return is made to the state-
ment following the PERFORM statement. If the THRU option is not specified,
the return follows execution of the last statement of the paragraph or section
referred to by procedure-name-I. If the THRU option is specified, the return
follows execution of the last statement of the paragraph or section referred to
by procedure-name-2.
The only relationship necessary between procedure-name-I and procedure-
name-2 is that a consecutive sequence of operations is
to
be execut8d
beginning at procedure-name-I and ending with the last statement in
procedure-name-2. GO TO and PERFORM statements may occur between
these limits.
If
there are two or more direct paths to the return point, then
procedure-name-2 may name a paragraph containing an EXIT statement, to
which all these paths must lead.
If control passes to these procedures by means other than a PERFORM state-
ment, it passes through the last statement of the procedure to the following
statement as if no PERFORM statement mentioned these procedures.
A procedure referenced by a PERFORM statement can include within it
another PERFORM statement only if the procedure associated with the
second PERFORM is entirely within or entirely without the procedure
referenced by the first PERFORM.
Correct Specifications
x PERFORM a THRU m
a------------.
d _PERFORM f THRU
j
f
m
-----------------~
x PERFORM a THRU m
a----------~
d PERFORM f THRU
j
h
m------------'
f
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