invokeOperation_t and invokeOperation_T

( $type, $value ) =
 $session->invokeOperation_t($object, $operation, \@args)

The invokeOperation_t() function is an alias for invoke_t(). The section “invoke_t and invoke_T” on page 98 provide additional information.

The invokeOperation_t() function is identical to invokeOperation(), except that the return indicates the type of the returned data as well.

 ( $type, $value ) = $session->invokeOperation_t(
    "Router::gw1", "makeInterface",
    [
    [ "INT", 1 ],
    [ "STRING", "interface-1" ],
    [ "STRING", "Interface" ]
    ] );

The “_T” variation also embeds type codes into the fields of returned complex structures.