>>SOURCE FORMAT IS FREE
*> cobol-perform-varying.cob - every common loop shape:
*>   PERFORM n TIMES, UNTIL with TEST BEFORE and TEST AFTER, inline
*>   VARYING over a table, nested VARYING ... AFTER, and EXIT PERFORM
*> Dialect: GnuCOBOL 3.x, free format
*> Status : desk-checked against the GnuCOBOL 3.2 Programmer's Guide;
*>          compiled and run with GnuCOBOL 3.2 on 2026-10-29
*> Inputs : none
*> Outputs: nine lines on standard output
*> Build  : cobc -x cobol-perform-varying.cob
*> Run    : ./cobol-perform-varying
*>          (Windows: cobol-perform-varying.exe)

IDENTIFICATION DIVISION.
PROGRAM-ID. PERFORM-DEMO.

ENVIRONMENT DIVISION.

DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-Counter        PIC 9(2) VALUE 0.
01 WS-Idx            PIC 9(2).
01 WS-Row            PIC 9.
01 WS-Col            PIC 9.
01 WS-Total          PIC 9(4) VALUE 0.
01 WS-Squares.
   05 WS-Square      PIC 9(3) OCCURS 5 TIMES.
01 WS-Grid-Data      PIC X(12) VALUE "ABCDEFGHIJKL".
01 WS-Grid REDEFINES WS-Grid-Data.
   05 WS-Grid-Row OCCURS 3 TIMES.
      10 WS-Cell     PIC X OCCURS 4 TIMES.

PROCEDURE DIVISION.
MAIN-PARAGRAPH.
*>  1. Out-of-line PERFORM, a fixed number of times.
    PERFORM SHOW-TICK 3 TIMES

*>  2. UNTIL with the default TEST BEFORE: condition already true,
*>     so the body never runs.
    MOVE 10 TO WS-Counter
    PERFORM WITH TEST BEFORE UNTIL WS-Counter >= 10
        DISPLAY "test-before body ran"
    END-PERFORM

*>  3. UNTIL with TEST AFTER: the body always runs at least once.
    PERFORM WITH TEST AFTER UNTIL WS-Counter >= 10
        DISPLAY "test-after body ran once"
    END-PERFORM

*>  4. Inline VARYING over a five-element table.
    PERFORM VARYING WS-Idx FROM 1 BY 1 UNTIL WS-Idx > 5
        COMPUTE WS-Square(WS-Idx) = WS-Idx * WS-Idx
        ADD WS-Square(WS-Idx) TO WS-Total
    END-PERFORM
    DISPLAY "Sum of squares 1..5 : " WS-Total
    DISPLAY "Index after the loop: " WS-Idx

*>  5. Nested VARYING ... AFTER over a 3-row by 4-column grid.
    PERFORM VARYING WS-Row FROM 1 BY 1 UNTIL WS-Row > 3
            AFTER   WS-Col FROM 1 BY 1 UNTIL WS-Col > 4
        DISPLAY WS-Cell(WS-Row, WS-Col) WITH NO ADVANCING
    END-PERFORM
    DISPLAY SPACE

*>  6. EXIT PERFORM leaves an inline loop early.
    PERFORM VARYING WS-Idx FROM 1 BY 1 UNTIL WS-Idx > 5
        IF WS-Square(WS-Idx) > 10
            DISPLAY "First square over 10: " WS-Square(WS-Idx)
            EXIT PERFORM
        END-IF
    END-PERFORM
    STOP RUN.

SHOW-TICK.
    ADD 1 TO WS-Counter
    DISPLAY "tick " WS-Counter.