/usr/include/muParser/ is in libmuparser-dev 1.34-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/muParser/muParser.h
/usr/include/muParser/muParserBase.h
/usr/include/muParser/muParserBytecode.h
/usr/include/muParser/muParserCallback.h
/usr/include/muParser/muParserComplex.h
/usr/include/muParser/muParserDLL.h
/usr/include/muParser/muParserDef.h
/usr/include/muParser/muParserError.h
/usr/include/muParser/muParserFixes.h
/usr/include/muParser/muParserInt.h
/usr/include/muParser/muParserStack.h
/usr/include/muParser/muParserTest.h
/usr/include/muParser/muParserToken.h
/usr/include/muParser/muParserTokenReader.h