Considering we have an association like:

asc1 =  <|"a.s.r"->1, "a.s.r345" -> 45, "asc" -> "cas", "qwrs" -> 78, "a.s.r[4]/vu" -> 4, "es" -> 74|>

How to extract an asc2 to include only the pairs where key starts with "a.s.r", as the following:

asc2 = <|"a.s.r"->1, "a.s.r345" -> 45, "a.s.r[4]/vu" -> 4|>

Thank you!