Power query parameter to select result

Hi, in excel, which I've included, I have a formula to pick out the alphabet, numbers or sprcial characters from a string.
and the reusult is determined by switch looking to a drop down list,

I have tried to create this so ;

 Table.AddColumn(Source, "Custom", each let
 ttolist = 
Text.ToList( [Text] ), alltext  = List.RemoveMatchingItems( ttolist, { "0".."9"} ), 
numbers = 
List.RemoveMatchingItems( ttolist, alltext ) , 
special =  List.RemoveMatchingItems(  List.Transform(  alltext, (A)=> Text.Lower(A)) , {"a".."z"} ) , 
alpha = List.RemoveMatchingItems( alltext, special) 
in Text.Combine( special  ))

but the last part following the in I do not want hard coded I have created a paramer of the options, but this does not work when plugged into
text.combine, I have attached all this. I think the problem is that it sees the value from the parameter as "text", not referring to the variable,


I have tried putting it withing the let so simplified ;

 Table.AddColumn(#"Changed Type", "Custom", each let caps  =  Text.Split(  Text.Upper([Text]) ," ") ,
lower =  Text.Split( [Text], " ") , 
result = Text.Combine(  selectorparameter  ) 
in result  )

but this does not work either? help?

Richard.