Perl module for detecting ignorable whitespace

 The XML::Filter::DetectWS module is a PerlSAX filter that detects which
 character data contains ignorable whitespace and optionally filters it.
 .
 The XML spec defines ignorable whitespace as the character data found
 in elements that were defined in an <!ELEMENT> declaration with a model
 of 'EMPTY' or 'Children' (Children is the rule that does not contain
 '#PCDATA').
 .
 In addition, XML::Filter::DetectWS allows the user to define other
 whitespace to be ignorable. The ignorable whitespace is passed to
 the PerlSAX Handler with the ignorable_whitespace handler, provided
 that the Handler implements this method. Otherwise it is passed to
 the characters handler. If the SkipIgnorableWS is set, the ignorable
 whitespace is simply discarded. XML::Filter::DetectWS also takes
 xml:space attributes into account.
 .
 CDATA sections are passed in the standard PerlSAX way (i.e. with
 surrounding start_cdata and end_cdata events), unless the Handler
 does not implement these methods. In that case, the CDATA section is
 simply passed to the characters method.