[plt-scheme] Implementing constructors for environment interface

I have an interface , how can i implement a constructor extend-env* using a
list representation such that

(extend-env* (var1 ... vark) (val1 ... valk)  f ) = g,

where g(var) =vali if var = vari for some i such that 1 ≤ i ≤ k
f (var) otherwise
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