Note (probably harmless): No library found for -lX11 Note (probably harmless): No library found for -lXtst Writing Makefile for X11::GUITest Microsoft (R) Program Maintenance Utility Version 6.00.8168.0 Copyright (C) Microsoft Corp 1988-1998. All rights reserved. Math::BigInt: couldn't load specified math lib(s), fallback to Math::BigInt::FastCalc at C:/cpanrun/build/5-10-0/site/lib/Win32API/File.pm line 20 cp GUITest.pm blib\lib\X11\GUITest.pm AutoSplitting blib\lib\X11\GUITest.pm (blib\lib\auto\X11\GUITest) C:\cpanrun\build\5-10-0\bin\perl.exe C:\cpanrun\build\5-10-0\lib\ExtUtils\xsubpp -typemap C:\cpanrun\build\5-10-0\lib\ExtUtils\typemap -typemap typemap GUITest.xs > GUITest.xsc && C:\cpanrun\build\5-10-0\bin\perl.exe -MExtUtils::Command -e mv GUITest.xsc GUITest.c cl -c -I/usr/X11R6/include -Werror -MD -Zi -DNDEBUG -O1 -DVERSION=\"0.10\" -DXS_VERSION=\"0.10\" "-IC:\cpanrun\build\5-10-0\lib\CORE" -DNDEBUG GUITest.c Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 12.00.8804 for 80x86 Copyright (C) Microsoft Corp 1984-1998. All rights reserved. Command line error D2021 : invalid numeric argument '/Werror' NMAKE : fatal error U1077: 'cl' : return code '0x2' Stop.