rework eval loop to unwrap lists when function calls return

stdlib/list.go

@@ -61,6 +61,7 @@ func l_append(input *ast.Token, vars ast.VarTable, funcs ast.FuncTable) *ast.Tok
         iter = &((*iter).Next)
     }
     (*iter).Next = input.Next
+    input.Next = nil
 
-    return src.Inner.(*ast.Token)
+    return src
 }