/usr/include/xercesc/util/regx/ is in libxerces-c2-dev 2.8.0+deb1-3build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/xercesc/util/regx/ASCIIRangeFactory.hpp
/usr/include/xercesc/util/regx/BMPattern.hpp
/usr/include/xercesc/util/regx/BlockRangeFactory.hpp
/usr/include/xercesc/util/regx/CharToken.hpp
/usr/include/xercesc/util/regx/ClosureToken.hpp
/usr/include/xercesc/util/regx/ConcatToken.hpp
/usr/include/xercesc/util/regx/ConditionToken.hpp
/usr/include/xercesc/util/regx/Match.hpp
/usr/include/xercesc/util/regx/ModifierToken.hpp
/usr/include/xercesc/util/regx/Op.hpp
/usr/include/xercesc/util/regx/OpFactory.hpp
/usr/include/xercesc/util/regx/ParenToken.hpp
/usr/include/xercesc/util/regx/ParserForXMLSchema.hpp
/usr/include/xercesc/util/regx/RangeFactory.hpp
/usr/include/xercesc/util/regx/RangeToken.hpp
/usr/include/xercesc/util/regx/RangeTokenMap.hpp
/usr/include/xercesc/util/regx/RegularExpression.hpp
/usr/include/xercesc/util/regx/RegxDefs.hpp
/usr/include/xercesc/util/regx/RegxParser.hpp
/usr/include/xercesc/util/regx/RegxUtil.hpp
/usr/include/xercesc/util/regx/StringToken.hpp
/usr/include/xercesc/util/regx/Token.hpp
/usr/include/xercesc/util/regx/TokenFactory.hpp
/usr/include/xercesc/util/regx/TokenInc.hpp
/usr/include/xercesc/util/regx/UniCharTable.hpp
/usr/include/xercesc/util/regx/UnicodeRangeFactory.hpp
/usr/include/xercesc/util/regx/UnionToken.hpp
/usr/include/xercesc/util/regx/XMLRangeFactory.hpp
/usr/include/xercesc/util/regx/XMLUniCharacter.hpp