It's only a list assignment.

The right hand side is just a list, and arrays are flattened to lists.

And the => is not a key-value separator, but just a "fat comma" which auto quotes the LHS.

That's why stuff like

%h = ( %a , %b )

or

%h = ( "foo", 100 , "bar" , 333) #²

(or both)

work.

update

²) added example with comma instead of =>