```python
<execute_python>
# 1) Parse intent and quantities
import re
from tinydb import Query
import datetime

matches = re.findall(r'(\d+)\s+pairs?\s+of\s+(\w+)\s*sunglasses?', user_request, re.IGNORECASE)
if not matches:
    STATUS = "invalid_request"
    answer_text = "I can help with that—how many pairs would you like to purchase?"
    print(f"LOG: ACTION=read DRY_RUN=True STATUS={STATUS}")
else:
    # Normalize requested items
    requested = []
    for qty, name in matches:
        requested.append({"name": name.title(), "qty": int(qty)})
    # 2) Validate existence and stock
    missing = None
    insufficient = None
    for req in requested:
        Item = Query()
        docs = inventory_tbl.search(Item.name.test(lambda n, nm=req["name"]: n.lower() == nm.lower()))
        if not docs:
            missing = req["name"]
            break
        doc = docs[0]
        if doc["quantity_in_stock"] < req["qty"]:
            insufficient = {"name": req["name"], "available": doc["quantity_in_stock"]}
            break
    if missing:
        STATUS = "no_match"
        answer_text = f"Sorry, we don’t have {missing} sunglasses right now. Maybe try a different style?"
        print(f"LOG: ACTION=read DRY_RUN=True STATUS={STATUS}")
    elif insufficient:
        STATUS = "insufficient_stock"
        answer_text = f"We only have {insufficient['available']} pairs of {insufficient['name']} left; let me know if you’d like to adjust your order."
        print(f"LOG: ACTION=read DRY_RUN=True STATUS={STATUS}")
    else:
        # 3) Process purchase transactions
        STATUS = "success"
        balance = get_current_balance(transactions_tbl)
        for req in requested:
            Item = Query()
            doc = inventory_tbl.get(Item.name.test(lambda n, nm=req["name"]: n.lower() == nm.lower()))
            # Compute line total and new balance
            line_total = doc["price"] * req["qty"]
            balance_after = balance + line_total
            # Insert transaction row
            txn_id = next_transaction_id(transactions_tbl)
            transactions_tbl.insert({
                "transaction_id": txn_id,
                "customer_name": "ANONYMOUS",
                "transaction_summary": f"Purchase: {req['qty']} x {req['name']}",
                "transaction_amount": line_total,
                "balance_after_transaction": balance_after,
                "timestamp": datetime.datetime.now().isoformat()
            })
            # Update stock
            inventory_tbl.update(
                {"quantity_in_stock": doc["quantity_in_stock"] - req["qty"]},
                Item.item_id == doc["item_id"]
            )
            balance = balance_after
        answer_text = "Thank you! Your order for 3 Classic and 1 Aviator sunglasses has been placed."
        print(f"LOG: ACTION=mutate SHOULD_MUTATE=True STATUS={STATUS}")
</execute_python>
```