could also do map { (split(/:/, $_)) [0,2] } but that's not as clear that it's key/value pairs

This is indeed a good point, but if you're not too much concerned about it, then

my %hash=map +(split /:/)[0,2], <DATA>;
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would be shorter and clearer, IMHO. In particular a very nice point about $_ is that it is the "topicalizer" so that it's the default implicit argument of just so many "actions"...