code: func interpolationFuncSplit() ast.Function {
  	return ast.Function{
  		ArgTypes:   []ast.Type{ast.TypeString, ast.TypeString},
  		ReturnType: ast.TypeList,
  		Callback: func(args []interface{}) (interface{}, error) {
  			sep := args[0].(string)
  			s := args[1].(string)
  			elements := strings.Split(s, sep)
  			return stringSliceToVariableValue(elements), nil
  		},
  	}
  }
docs: // interpolationFuncSplit implements the "split" function that allows
  // strings to split into multi-variable values