I applied a patch (bug #32138) to my Windows build that included pixel-test results for my Mac build. When I tried to generate pixel test results on my Windows build, the following Perl warning was thrown: Use of uninitialized value $_ in pattern match (m//) at WebKitTools/Scripts/run-webkit-tests line 764. For your reference, after applying the patch and building WebKit (debug build), I used the following command line to run the test included in the patch: WebKitTools/Scripts/run-webkit-tests --debug --pixel --add-platform-exceptions LayoutTests/fast/lists/list-style-type-upper-greek.html