This works on Windows too, but the Windows shell (cmd.exe) only knows about double quotes:

o conf make '"C:\tmp\path with spaces\bin\nmake.exe"'
[download]

works and allows to use a directory with whitespace in its name. The same should also be done for the gzip and tar paths, and also for Perl itself (especially $^X :-) ). See also RT 17877 - the approach proposed by you to add quoting if it becomes necessary is what I do as well.