AB Iblocks

//Params:
$iblockA = 44;
$iblockB = 6;
$pregMatchStr = '#\((.*?)\)#';
$testCountElem = 10;
//Script:
CModule::IncludeModule('iblock');
$dbIblockB = CIblockElement::GetList([], ['IBLOCK_ID' => $iblockB], false, false, ['NAME', 'ID', 'XML_ID']);
$arNamesB = [];
$cnt = 0;
while($obB = $dbIblockB->GetNext()){
    preg_match($pregMatchStr, $obB['NAME'], $match);
    if(!empty($match) && !empty($match[1]))
        $arNamesB[$obB['XML_ID']] = $match[1];

    if((int)$testCountElem > 0 && $cnt++ > $testCountElem)
        break;
}

print_r($arNamesB);

$dbIblockA = CIblockElement::GetList([], ['IBLOCK_ID' => $iblockA, 'NAME' => $arNamesB], false, false, ['NAME', 'ID', 'XML_ID']);
$arNamesA = [];
while($obA = $dbIblockA->GetNext()){
    $arNamesA[$obA['ID']] = $obA['NAME'];
}
print_r($arNamesA);
$arNamesB = array_flip($arNamesB);
$el = new CIBlockElement;
foreach($arNamesA as $id => $name){
    if(isset($arNamesB[$name])){
        $el->Update($id, ['XML_ID' => $arNamesB[$name]]);
    }
}