I've read about this and (I think) managed it once.
I've certainly experienced all the wonderful sensations which normally accompany ejaculation without actually ejaculating and then done the same when I ejaculated, say, 5 minutes later. The one difference was that the first "orgasm" didn't lead to that physical relief/collapse sensation which is the "after dinner brandy" of the male sexual experience! If that had happened, it would have been difficult to maintain any concentration!
Normally, for men, "to come" is the term used for both orgasm and ejaculation (what a rare need to separate the two
), so it's a bit confusing to think of multiple orgasms.
Once ejaculation takes place, no man that I've ever heard of (without Viagra) can just continue humping and do it again!