Currently, the spot price (market price for bitcoin on exchanges) trades lower than futures prices. The spread for the June futures contract is more than 25 percent annualized on most major exchanges.
This means that anyone can buy bitcoin and use that bitcoin as collateral to sell the June futures contract. This trade locks in a risk-free 6 percent USD-denominated return (more than 25 percent annualized) no matter where the price of bitcoin goes over the following months.
The only risk is exchange custody (losing coins due to poor management or hacks).
If you go long on the perpetual swap, you are charged a funding rate every eight hours. This funding rate is set by the market to ensure the perpetual futures price stays near the index spot price. In a way, it is basically a futures contract that is only eight hours in duration and it always rolls over.
Over the last month, the perpetual swap has been averaging around 0.03 percent every eight hours, or 0.09 percent daily or 32.9 percent annually. This funding rate is the longs paying the shorts (because more capital is naturally going to be long bitcoin, especially when the price is going up).