I'm partial to:

# Append %add to %base:
@base{keys %add}= values %add;
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note that for duplicate keys, %add wins in this case, just as if you had done: %base= ( %base, %add ); but the hash slice code should be faster (tho I won't guarentee that, especially not for all cases) since it doesn't have to empty the first hash and then reload it with itself.

        - tye (but my friends call me "Tye")