diff -up doxygen/src/configimpl.l.orig doxygen/src/configimpl.l

--- doxygen/src/configimpl.l.orig	2021-01-19 17:25:00.933789247 +0100

+++ doxygen/src/configimpl.l	2021-01-19 17:26:09.704744240 +0100

@@ -1175,8 +1175,7 @@ static void substEnvVarsInStrList(String

   for (const auto &s : sl)

   {

     QCString result = s.c_str();

-    // an argument with quotes will have an extra space at the end, so wasQuoted will be TRUE.

-    bool wasQuoted = (result.find(' ')!=-1) || (result.find('\t')!=-1);

+    bool wasQuoted = (result.find(' ')!=-1) || (result.find('\t')!=-1) || (result.find('"')!=-1);

     // here we strip the quote again

     substEnvVarsInString(result);

@@ -1229,7 +1228,7 @@ static void substEnvVarsInStrList(String

       }

       if (p!=l) // add the leftover as a string

       {

-        results.push_back(result.right(l-p).data());

+        results.push_back(result.right(l-p).str());

       }

     }

     else // just goto the next element in the list