One interesting thing I've got stucked on - if we have some multilevel arrays/hashes (which aren't the same in perl), there is no standard way to change all the object's values. The only thing I've found usefull is
map function, which nevertheless works only for map arrays. However, it could be very usefull, to have a possibility to change each scalar element of some multilevel object. For example, if you ever used XML::Simple, you could observe the following behavior with values, which contain new lines.
XML:
<root>
<elem>asdf</elem>
</root>