IDENTIFICATION DIVISION.
       PROGRAM-ID. ProgStructEdge.
      *> ============================================================
      *> 程序構造境界テスト (Program Structure Edge Cases)
      *> レガシーCOBOL構造: PERFORM THRU, GO TO DEPENDING ON,
      *> 段落スルー, ALTER(非推奨), 複数SECTION
      *> ============================================================

       ENVIRONMENT DIVISION.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 WS-SWITCH        PIC X(1) VALUE 'N'.
           88 WS-ON        VALUE 'Y'.
       01 WS-COUNT         PIC 9(5) VALUE 0.
       01 WS-GO-TO-IDX     PIC 9(1) VALUE 0.
       01 WS-PASS          PIC 9(2) VALUE 0.
       01 WS-FAIL          PIC 9(2) VALUE 0.

       PROCEDURE DIVISION.
       MAIN.
           DISPLAY "PROG-STRUCT-EDGE: Program structure edge tests"

      *> Test 1: PERFORM THRU (段落範囲実行)
           ADD 1 TO WS-COUNT.
           DISPLAY "T1-THRU: PERFORM THRU para range"
           PERFORM PARA-A THRU PARA-C
           DISPLAY "T1-THRU: PASS"
           ADD 1 TO WS-PASS.

      *> Test 2: 段落スルー (Paragraph fall-through)
           ADD 1 TO WS-COUNT.
           DISPLAY "T2-FALL: Paragraph fall-through (A->B)"
           PERFORM PARA-D THRU PARA-E
           DISPLAY "T2-FALL: PASS"
           ADD 1 TO WS-PASS.

      *> Test 3: GO TO DEPENDING ON
           ADD 1 TO WS-COUNT.
           DISPLAY "T3-GOTO: GO TO DEPENDING ON"
           MOVE 0 TO WS-GO-TO-IDX.
           GO TO PARA-X PARA-Y PARA-Z
               DEPENDING ON WS-GO-TO-IDX.
      *> WS-GO-TO-IDX=0 → 次段落へ (何も実行しない)
           DISPLAY "T3-GOTO: IDX=0 skipped (PASS)"
           ADD 1 TO WS-PASS.

           MOVE 2 TO WS-GO-TO-IDX.
           GO TO PARA-X PARA-Y PARA-Z
               DEPENDING ON WS-GO-TO-IDX
           .  *> ここには来ない

      *> Test 4: GO TO (単純)
           ADD 1 TO WS-COUNT.
           DISPLAY "T4-GOTO-SIMPLE: Simple GO TO"
           GO TO PARA-END-T4.
           DISPLAY "T4-GOTO: FAIL - should not reach"
           ADD 1 TO WS-FAIL.
           GO TO PARA-END-T4-EXIT.

       PARA-END-T4.
           DISPLAY "T4-GOTO-SIMPLE: PASS"
           ADD 1 TO WS-PASS.

       PARA-END-T4-EXIT.
           CONTINUE.

      *> Test 5: EXIT PARAGRAPH vs EXIT SECTION
           ADD 1 TO WS-COUNT.
           DISPLAY "T5-EXIT: EXIT PARAGRAPH"
           PERFORM PARA-EXIT-DEMO
           DISPLAY "T5-EXIT: PASS"
           ADD 1 TO WS-PASS.

      *> Test 6: ALTER (非推奨だがレガシーCOBOLに存在)
           ADD 1 TO WS-COUNT.
           DISPLAY "T6-ALTER: ALTER (legacy)"
           ALTER PARA-ALTER-TARGET TO PROCEED TO PARA-ALTER-OK
           GO TO PARA-ALTER-TARGET.

       PARA-ALTER-TARGET.
           DISPLAY "T6-ALTER: FAIL - old path"
           ADD 1 TO WS-FAIL.
           GO TO PARA-ALTER-DONE.

       PARA-ALTER-OK.
           DISPLAY "T6-ALTER: PASS"
           ADD 1 TO WS-PASS.

       PARA-ALTER-DONE.
           CONTINUE.

      *> Summary
           DISPLAY " "
           DISPLAY "PROG-STRUCT-EDGE: PASS=" WS-PASS " FAIL=" WS-FAIL
           IF WS-FAIL = 0
               DISPLAY "ALL PASSED"
               STOP RUN RETURNING 0
           ELSE
               STOP RUN RETURNING 1
           END-IF
           .

      *> === PERFORM THRU 段落群 ===
       PARA-A.
           DISPLAY "  PARA-A: start"
           .
       PARA-B.
           DISPLAY "  PARA-B: middle (THRU includes)"
           .
       PARA-C.
           DISPLAY "  PARA-C: end (THRU target)"
           .

      *> === 段落スルー デモ ===
       PARA-D.
           DISPLAY "  PARA-D: fall through to PARA-E"
           .
       PARA-E.
           DISPLAY "  PARA-E: reached via fall-through"
           .

      *> === GO TO DEPENDING ON 飛び先 ===
       PARA-X.
           DISPLAY "  PARA-X: IDX=1"
           .
       PARA-Y.
           DISPLAY "  PARA-Y: IDX=2"
           .
       PARA-Z.
           DISPLAY "  PARA-Z: IDX=3"
           .

      *> === EXIT PARAGRAPH デモ ===
       PARA-EXIT-DEMO.
           DISPLAY "  Before EXIT PARAGRAPH"
           IF WS-PASS >= 0
               EXIT PARAGRAPH
           END-IF
           DISPLAY "  After EXIT PARAGRAPH (NOT reached)"
           .

       END PROGRAM ProgStructEdge.