st: merge command when variable already defined

[Rufus Peabody <rufus.peabody@gmail.com>]

I have a variable that contains values for most of my dataset.  I  
would like to add values where it is presently undefined by match  
merging with another dataset.  However, this does not work since the  
variable is already defined.  The only way around this that I can see  
is to simply delete the variable entirely.  Is there any way around  
this?

Thanks,
Rufus
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