docs: Add GOTO keyword documentation with migration guidance to ON patterns
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src/06-gbdialog/keyword-goto.md
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src/06-gbdialog/keyword-goto.md
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# GOTO Keyword
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> ⚠️ **WARNING: GOTO is supported but NOT RECOMMENDED**
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>
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> While GOTO works for backward compatibility, you should use **event-driven patterns with the ON keyword** instead. GOTO makes code harder to maintain and debug.
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## Syntax
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```basic
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label:
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' statements
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GOTO label
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IF condition THEN GOTO label
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```
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## Description
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`GOTO` transfers program execution to a labeled line. Labels are identifiers followed by a colon (`:`) at the start of a line.
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**This keyword exists for backward compatibility only.** Modern General Bots code should use:
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- `ON INSERT/UPDATE/DELETE OF` for event-driven programming
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- `WHILE ... WEND` for loops
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- `FOR EACH ... NEXT` for iteration
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- `SUB` / `FUNCTION` for code organization
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---
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## ❌ OLD WAY vs ✅ NEW WAY
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### Polling Loop (Don't Do This)
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```basic
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' ❌ BAD: GOTO-based polling loop
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mainLoop:
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leads = FIND "leads", "processed = false"
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FOR EACH lead IN leads
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CALL processLead(lead)
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NEXT lead
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WAIT 5
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GOTO mainLoop
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```
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### Event-Driven (Do This Instead)
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```basic
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' ✅ GOOD: Event-driven with ON keyword
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ON INSERT OF "leads"
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lead = GET LAST "leads"
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score = SCORE LEAD lead
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IF score.status = "hot" THEN
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TALK TO "whatsapp:" + sales_phone, "🔥 Hot lead: " + lead.name
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END IF
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END ON
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```
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---
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## Why ON is Better Than GOTO
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| Aspect | GOTO Loop | ON Event |
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|--------|-----------|----------|
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| **Efficiency** | Polls constantly, wastes CPU | Triggers only when data changes |
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| **Code clarity** | Spaghetti code, hard to follow | Clear cause-and-effect |
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| **Resource usage** | Always running | Idle until triggered |
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| **Scalability** | Degrades with more data | Handles scale naturally |
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| **Debugging** | Hard to trace execution | Clear event flow |
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| **LLM integration** | Poor | Works well with TOOLs |
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---
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## If You Must Use GOTO
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For legacy code migration or specific use cases, GOTO is supported:
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### Simple Loop
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```basic
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counter:
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TALK "Count: " + x
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x = x + 1
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IF x < 5 THEN GOTO counter
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TALK "Done!"
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```
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### Multiple Labels
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```basic
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start:
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TALK "Starting..."
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GOTO process
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error:
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TALK "An error occurred"
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GOTO cleanup
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process:
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result = DO_SOMETHING
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IF result = "error" THEN GOTO error
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TALK "Success!"
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GOTO cleanup
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cleanup:
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TALK "Cleaning up..."
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```
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### Conditional GOTO
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```basic
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check:
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IF temperature > 30 THEN GOTO too_hot
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IF temperature < 10 THEN GOTO too_cold
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TALK "Temperature is comfortable"
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GOTO done
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too_hot:
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TALK "Warning: Too hot!"
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GPIO SET fan_pin, HIGH
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GOTO done
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too_cold:
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TALK "Warning: Too cold!"
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GPIO SET heater_pin, HIGH
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GOTO done
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done:
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TALK "Check complete"
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```
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---
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## How GOTO Works Internally
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GOTO is **not native to the Rhai engine**. General Bots transforms GOTO-based code into a state machine:
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```basic
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' Your code:
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loop:
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x = x + 1
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IF x < 3 THEN GOTO loop
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TALK "Done"
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```
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```basic
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' Transformed internally to:
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let __goto_label = "loop"
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while __goto_label != "__exit" {
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if __goto_label == "loop" {
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x = x + 1
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if x < 3 { __goto_label = "loop"; continue; }
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TALK "Done"
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__goto_label = "__exit"
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}
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}
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```
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This transformation:
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- Adds overhead compared to native loops
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- Has a safety limit of 1,000,000 iterations to prevent infinite loops
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- Emits warnings in the server logs recommending ON patterns
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---
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## Limitations
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| Limitation | Description |
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|------------|-------------|
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| **No computed GOTO** | `GOTO variable` is not supported |
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| **No GOSUB** | Use `SUB` / `CALL` instead |
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| **No line numbers** | Only named labels are supported |
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| **Performance** | Slower than native WHILE loops |
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| **Iteration limit** | Maximum 1,000,000 iterations per GOTO loop |
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---
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## Migration Guide
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### From GOTO Loop to WHILE
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```basic
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' Before (GOTO):
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start:
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TALK "Hello"
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x = x + 1
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IF x < 10 THEN GOTO start
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' After (WHILE):
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WHILE x < 10
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TALK "Hello"
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x = x + 1
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WEND
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```
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### From GOTO Loop to ON Event
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```basic
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' Before (GOTO polling):
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checkOrders:
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orders = FIND "orders", "status = 'new'"
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FOR EACH order IN orders
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CALL processOrder(order)
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NEXT order
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WAIT 10
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GOTO checkOrders
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' After (ON event):
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ON INSERT OF "orders"
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order = GET LAST "orders"
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IF order.status = "new" THEN
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CALL processOrder(order)
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END IF
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END ON
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```
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### From GOTO Error Handling to ON ERROR
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```basic
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' Before (GOTO):
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result = RISKY_OPERATION
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IF result = "error" THEN GOTO handleError
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TALK "Success"
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GOTO done
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handleError:
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TALK "Failed!"
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done:
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' After (ON ERROR):
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ON ERROR RESUME NEXT
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result = RISKY_OPERATION
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IF ERROR THEN
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TALK "Failed!"
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ELSE
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TALK "Success"
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END IF
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ON ERROR GOTO 0
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```
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---
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## Best Practices
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1. **Don't use GOTO for new code** - Use WHILE, FOR EACH, ON, or SUB/FUNCTION
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2. **Migrate existing GOTO code** - Refactor to event-driven patterns when possible
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3. **If you must use GOTO** - Keep it simple, avoid deep nesting
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4. **Add comments** - Explain why GOTO is necessary
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5. **Set reasonable limits** - Don't rely on the 1M iteration safety limit
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---
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## See Also
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- [ON Keyword](./keyword-on.md) - **Recommended**: Event-driven programming
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- [WHILE ... WEND](./keyword-while.md) - Loop construct
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- [FOR EACH ... NEXT](./keyword-for-each.md) - Iteration
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- [SUB / FUNCTION](./keyword-sub.md) - Code organization
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- [ON ERROR](./keyword-on-error.md) - Error handling
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---
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## Summary
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| Use Case | Instead of GOTO, Use |
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|----------|---------------------|
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| Polling for changes | `ON INSERT/UPDATE/DELETE OF` |
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| Repeating code | `WHILE ... WEND` |
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| Iterating collections | `FOR EACH ... NEXT` |
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| Reusable code blocks | `SUB` / `FUNCTION` + `CALL` |
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| Error handling | `ON ERROR RESUME NEXT` |
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| Conditional branching | `IF ... ELSEIF ... ELSE ... END IF` |
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| Multiple conditions | `SWITCH ... CASE ... END SWITCH` |
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**The ON keyword is the future. GOTO is the past.**
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@ -84,6 +84,7 @@ See [Script Execution Flow](./script-execution-flow.md) for complete details.
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| `FORMAT` | Data | Format strings and dates |
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| `GENERATE PDF` | Files | Generate PDF from template |
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| `GET` | Variables | Get variable or API data |
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| `GOTO` | Control | Jump to label (⚠️ use ON instead) |
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| `GET BOT MEMORY` | Memory | Retrieve bot-level persisted data |
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| `GET USER MEMORY` | Memory | Retrieve user-level persisted data (cross-bot) |
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| `GRAPHQL` | HTTP | Execute GraphQL query |
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