Can't build Qt in Windows from source, Perl installed but still can't find headers

[MattPhillips]

I'm using Cygwin on Windows 7, 64-bit. I downloaded the 4.8.3. source and followed the instructions here, putting `<qtdir>/bin` in PATH along with the path to my chosen compiler. Configure fails immediately,

$ ./configure

Creating qmake. Please
wait... g++ -c -o makefile.o -pipe -DQMAKE_OPENSOURCE_EDITION -g -I.
-Igenerators -Igenerators/unix -Igenerators/win32 -Igenerators/mac -Igenerators/symbian -Igenerators/integrity -I/cygdrive/c/Qt/4.8.3/include -I/cygdrive/c/Qt/4.8.3/include/QtCore -I/cygdrive/c/Qt/4.8.3/src/corelib/global -I/cygdrive/c/Qt/4.8.3/src/corelib/xml -I/cygdrive/c/Qt/4.8.3/tools/shared -DQT_NO_PCRE -DQT_BUILD_QMAKE -DQT_BOOTSTRAPPED -DQLIBRARYINFO_EPOCROOT -DQT_NO_TEXTCODEC -DQT_NO_UNICODETABLES -DQT_NO_COMPONENT -DQT_NO_STL -DQT_NO_COMPRESS -I/cygdrive/c/Qt/4.8.3/mkspecs/cygwin-g++ -DHAVE_QCONFIG_CPP -DQT_NO_THREAD -DQT_NO_QOBJECT -DQT_NO_GEOM_VARIANT -DQT_NO_DEPRECATED generators/makefile.cpp

In file included from ./option.h:45:0,
from generators/makefile.h:45,
from generators/makefile.cpp:42: ./project.h:45:25: fatal error: qstringlist.h: No such file or directory compilation
terminated. make: *** [makefile.o] Error 1

Discussions here and here identify the problem as being with Perl; however Perl is on my system and on the path. To be sure I went and downloaded/installed ActivePerl, after which I added `Perl64/bin` to the path. Same result.

$ whereis perl

perl: /bin/perl.exe /usr/bin/perl.exe /usr/share/perl
/cygdrive/c/Perl64/bin/perl.exe /cygdrive/c/Perl64/bin/perl516.dll


$ echo $PATH

/cygdrive/c/Perl64/bin:/cygdrive/c/gcc/bin:/bin: ...
/cygdrive/c/Qt/4.8.3/bin

Would very much appreciate some help out with this. qstringlist.h resides in include/QtCore which is explicitly included in the initial g++ command that fails saying it can't find it, so what to do?