Passing parameters of any type may be accomplished using the keyword ANY as the passed value type:

DefinitionName ( ANY AliasName ) := expression;

a := 10;
b := 20;
c := '1';
d := '2';
e := '3';
f := '4';
s1 := [c,d];
s2 := [e,f];

ds1 := DATASET(s1,{STRING1 ltr});
ds2 := DATASET(s2,{STRING1 ltr});

MyFunc(ANY l, ANY r) := l + r;

MyFunc(a,b);      //returns 30
MyFunc(a,c);      //returns '101'
MyFunc(c,d);      //returns '12'
MyFunc(s1,s2);    //returns a set: ['1','2','3','4']
MyFunc(ds1,ds2);  //returns 4 records: '1', '2', '3', and '4'