Everything chromatic says, but also, I thought I'd add that hash slices are very useful for stuffing an array into a hash (as in the original example). For example, say that you had a list of elements and you wanted to check if certain items were in that list. The best way to do this is with a hash, generally, and it's very easy to set up such a hash for lookups:

my @list = qw/foo bar baz/;

my %hash;
@hash{@list} = ();

# now I can test if an element is in @list
# by checking if the key exists in %hash
if (exists $hash{"foo"}) {
    print "found foo!";
}
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