1+2/3*4${expression} in ${filter key word}
calculate currency exchange expression

find target currency with filter
currency rate will be queried every 24 hours to reduce API usage.
There's a currency exchange function out of box in Raycast's Calculator.
You can type like 12 usd in gbp to show the currency exchange result.
In some case, when you exactly know the currency code, it works fine, but it still has some challanges:
KRW, the W is from Won in Korea, not easy to understand.