There are biscuits on the sideboard if you want them. That’s a natural-enough-sounding expression, but it’s also a peculiar thing to say.

“[T]he verb is the highly ordinary are,” noted philosopher J.L. Austin in 1956, “but the if is more like that in ‘I can if I choose’ than that in ‘I panted if I ran’: for we can certainly infer from it that ‘There are biscuits on the sideboard whether you want them or not’ and that anyway ‘There are biscuits on the sideboard’, whereas it would be folly to infer that ‘If there are no biscuits on the sideboard you do not want them’, or to understand the meaning to be that you have only to want biscuits to cause them to be on the sideboard.”

Delightfully, such expressions are called biscuit conditionals.