Teiid 8.11 adds the ability to define virtual functions using the standard procedure syntax:

create virtual function my-func (param1 string) returns string as
return param1 || 'abc';;

If function class/method metadata is also defined, it will not be used. Only in and a return parameter are supported. There is not yet a restriction on the definition (a single statement is shown above, but could be a block), but following other databases we may limit the type of statements that are allowed.