This is how it's done (note the 2 variables $clAttrModifiers and $vanprijsFeature):
$lang=nl
$productCatalog=myProductCatalog
$catalogVersion=catalogversion(catalog(id[default=$productCatalog]),version[default='Staged'])[unique=true,default=$productCatalog:Staged]
$approved=approvalstatus(code)[default='check']
$baseProduct=baseProduct(code,$catalogVersion)
$clAttrModifiers=system='MySystemClassifications',version='General',translator=de.hybris.platform.catalog.jalo.classification.impex.ClassificationAttributeTranslator,lang=nl
$vanprijsFeature=@Vanprijs[$clAttrModifiers];
INSERT_UPDATE Product;code[unique=true];$vanprijsFeature;$catalogVersion
;M300047;200.59;