Welcome to complex datastructures.

my @items = @{$rss->{items}}; means this: Start with the hashref held in $rss. Dereferece that hashref, inspecting the content of $rss->{items}. Apparently $rss->{items} contains an array reference. The array reference is dereferenced with @{....}. And the resulting list is assigned to @items.

Later, $item->{'title'} is dereferencing the hashref held in $item. The value held in $item->{'title'} is apparently...the title. ;)

See perlreftut, perllol, and perlref for some informative reading.