@saw{ @arr } = ();  # The line I'm not understanding

##</code><code>##

{};                             # hash reference
[];                             # array reference
%hash;                          # named hash
$hash{'foo'} = 'bar';           # left-hand-side (LHS) of '=' in scalar context
@ary = (1,2,3);                 # LHS & RHS are in list context:
                                #    assign a list to an array named 'ary'

$hash{'foo'} = @ary;            # LHS context(scalar) forces RHS scalar context:
                                #    $hash{'foo'} == 3 , i.e. scalar(@ary)

@hash{qw(foo bar quux)} = @ary; # LHS in list context, RHS in list context:
                                #    $hash{'bar'} == 2; $hash{'quux'} == 3