II thougt that عَفْواً meant pardon ( from the verb عافَ ), and أَهلاً is like "welcome, you are welcome". Of course it can be translate as " ello", but welcome may also be use. Is it true or not ?
عفوا can mean "excuse me" and "welcome" (for thanks) and even "sorry" - and it is from the verb عفا (to forgive)
أهلا is mainly welcome ... or in the sense of Hello ... i rarely hear people use it for "you are welcome" (as a reply to thanks) - some people do but not many and probably more locally in some places.