That was exactly what my suspicions were above! Note the problem is specific to Marketo's Velocity config, not to Velocity in general. Normally (when Velocity is used in Java-based websites, for example), while neither a Java variable nor a corresponding VTL reference ( $something ) can start with a number, you can still have a key within the Velocity $context reference that starts with a number. That is, if you access it as $99something , you will fail, but if you make sure to use bracketed-key syntax $context["99something"] all the time, it will work. However, Marketo is doing some kind of pre- or post-processing that makes it not work here, even w/brackets. And as you say, COs with numeroalphabetic names shouldn't be allowed because of this incompatibility.
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