Firstly, it operates on a XML::LibXML DOM. Assuming you've already got
that DOM in memory, XML::LibXML::PrettyPrint won't *add* much to your
memory usage.
Secondly, the DESCRIPTION section in the documentation makes it clear
that this module is designed for pretty rare cases, and that most of the
time you're better off not pretty-printing your XML at all.
Thirdly, the style of indentation it offers wouldn't work well with a
stream-based XML parser, as in some cases it needs to be able to do look
aheads. e.g. when processing an element of category EL_COMPACT it needs
to check if any of its descendants are EL_BLOCK. Yes, that's possible
with a stream-based parser, but it's quite fiddly.
So I'm afraid this is a "WONTFIX".
