# read XML file in $xml_string

my $out='';
while($xml_string=~s!^(.*?<property>\s*)(<\?xml.+?>)(\s*</property>)!!s){
  $out.=$1.'<![CDATA[';
  my ($in,$after)=($2,$3);
  $in=~s/\Q]]>\E/]]]><![CDATA[]>/gs;
  $out.=$in.']]>'.$after;
}
$xml_string=$out.$xml_string;
$out='';

# parse XML $xml_string ...