%hash;                 # a hash
$hash{$foo} = 'bar';   # used in scalar context
@ary = qw(foo bar baz);
$hash{@ary}++;         # key is scalar(@ary) here: $hash{3} == 1;
@hash{@ary} = (1,2,3); # hash is now (foo=>1,bar=>2,baz=3)
@hash{@ary}++;         # $hash{baz} == 4; # why?

##</code><code>##

@hash{@array} = (1) x scalar(@array);