fnSwitch.pq

let
  fnSwitch = (string as text, switches as list, default as any) =>
    let
      // Get max index of replacement list
      Max = List.Count(switches) - 1, 
      // Use List.Accumulate to loop through replacements
      Switch = List.Accumulate(
        switches, 
        default, 
        // if the string matches first index, then replace with second item in that nested list
        // else keep the default
        (state, current) => if string = current{0} then current{1} else state
      )
    in
      Switch, 

  // Documentation
  fnType = type function (string as text, switches as list, default as text) as any
    meta [
      Documentation.Name = "fnSwitch", 
      Documentation.LongDescription
        = "This function takes a string and performs a SWITCH replacement using nested lists. Additionally, it provides a default value if there are no matches."
    ]
in
  Value.ReplaceType(fnSwitch, fnType)