Hi Daniel!
Munctions were promising, but are now discontinued, so any threads about them tend to meander into discussions of webhook-based alternatives. The Excel function simulator you tried is one, though I find its syntax unsuitable for all but the most basic tasks (this is not a hit on the service, as it also applies to Excel itself -- thus why VBA is preferred for Excel power users). Rajesh (who responded above) has another one, BrightHooks, which offers a built-in function for your phone number task, so give him a shout.
FlowBoost is way more than a set of data cleansing functions (though we do bundle some industry-standard libraries like Google's Phone Number validator). Rather, FB is a full-fledged scripting environment for use in Marketo Flows. Anything you can do with variables in JavaScript -- i.e. anything at all -- you can do w/FB. With the Pro version, you can perform almost magical things, like sorting leads by percentiles (think top 25% of leads by number of site visits) and getting deep insight into lead domains.
However, though it's been live for over a year for in-house clients (small to multinational, serving millions of requests per month) it's somewhat of a secret project from a commercial standpoint. As tech lead, I blog about new features over at http://blog.teknkl.com/tag/flowboost. But to get a trial key, you should hit up eunthank@etumos.com. I sometimes answer Community questions with ways you could do things in FlowBoost/JS, not because... okay, not only because!... I'm bigging up the service, but because that's literally the way I'd attack the problem if it were for our clients, rather than building a new app every time.
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