The decision on the proportion of hybrid bonds in the capital structure for Eni S.p.A. as of the end of 2022 should consider the company's financial performance, liquidity, and the changing interest rate environment.

1.  **Profitability and Cash Flow:** Eni demonstrated a strong recovery in 2022, with a profit attributable to owners of the parent of 13.887 billion EUR, compared to 5.821 billion EUR in 2021. Cash flow from operating activities was robust at 17.46 billion EUR, significantly strengthening its ability to cover debt service obligations.
2.  **Market Environment:** The data provided shows a significant shift in swap rates (5Y, 7Y, and 10Y) from negative/low values in 2020-2021 to much higher levels in 2022 (e.g., 10Y swap rising to 1.927%). Higher interest rates increase the cost of traditional debt and make the equity-like features of hybrid bonds more expensive to service, while also potentially impacting the valuation of debt instruments.
3.  **Capital Structure Management:** Eni has shown proactive management of perpetual subordinated bonds, including issuing and redeeming these instruments to optimize its capital structure. As of 2022, the company has high levels of cash (10.155 billion EUR) and a solid equity base (55.23 billion EUR). Given the current strong profitability and the increased cost of debt financing, excessive reliance on hybrid bonds (which carry higher interest costs than senior debt) is suboptimal. 
4.  **Strategic Balance:** A modest use of hybrid capital (25%) is appropriate to maintain financial flexibility, preserve credit ratings, and avoid the dilution of common equity, while avoiding the higher cost and complexity associated with a more aggressive 50-75% hybrid structure. Given the company's strong cash position and operating cash flow, it does not require a high reliance on expensive hybrid instruments to remain solvent or fund operations.

<answer>25%</answer>